finding a tangent line to a parabolaHow do I find the equation of a tangent line to a curve?Find intersection(s) between parametrized parabola and a lineIntersection point of tangent line with $X$ axisderive a parabola from two tangent linesWhy is this answer wrong? (point of intersection between parabola and line)Two questions on finding the equation of a parabola word problem- Klein's Calculus: An Intuitive and Physical ApproachEuclid 1999 Question 4(a) - Circle Tangent IntersectionFinding the Equation for the Line Tangent to a Parabola At a Given PointMirror image of the parabola about a tangentMaximizing $x^2 y + y^2 z + z^2 x − x^2 z − y^2 x − z^2 y$ for $x$, $y$, $z$ between $0$ and $1$ (inclusive)Find the numerical value of this expression

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finding a tangent line to a parabola


How do I find the equation of a tangent line to a curve?Find intersection(s) between parametrized parabola and a lineIntersection point of tangent line with $X$ axisderive a parabola from two tangent linesWhy is this answer wrong? (point of intersection between parabola and line)Two questions on finding the equation of a parabola word problem- Klein's Calculus: An Intuitive and Physical ApproachEuclid 1999 Question 4(a) - Circle Tangent IntersectionFinding the Equation for the Line Tangent to a Parabola At a Given PointMirror image of the parabola about a tangentMaximizing $x^2 y + y^2 z + z^2 x − x^2 z − y^2 x − z^2 y$ for $x$, $y$, $z$ between $0$ and $1$ (inclusive)Find the numerical value of this expression













5












$begingroup$


I am practicing for a math contest and I encountered the following problem that I don't know how to solve:



For which value of $b$ is there only one intersection between the line $y = x + b$ and the parabola $y = x^2 + 5x + 3$?



How do I solve it?



Edit:
I made a mistake typing the problem. It should be $y = x^2 - 5x + 3$ instead of $y = x^2 + 5x + 3 $ the answer key says the answer is -6.










share|cite|improve this question











$endgroup$







  • 1




    $begingroup$
    Do you know how to find a derivative?
    $endgroup$
    – R. Burton
    Apr 25 at 0:13






  • 7




    $begingroup$
    Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
    $endgroup$
    – the_fox
    Apr 25 at 0:14






  • 2




    $begingroup$
    @NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
    $endgroup$
    – amd
    Apr 25 at 1:37






  • 1




    $begingroup$
    @NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
    $endgroup$
    – amd
    Apr 25 at 3:32







  • 2




    $begingroup$
    If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
    $endgroup$
    – YawarRaza7349
    Apr 25 at 3:55















5












$begingroup$


I am practicing for a math contest and I encountered the following problem that I don't know how to solve:



For which value of $b$ is there only one intersection between the line $y = x + b$ and the parabola $y = x^2 + 5x + 3$?



How do I solve it?



Edit:
I made a mistake typing the problem. It should be $y = x^2 - 5x + 3$ instead of $y = x^2 + 5x + 3 $ the answer key says the answer is -6.










share|cite|improve this question











$endgroup$







  • 1




    $begingroup$
    Do you know how to find a derivative?
    $endgroup$
    – R. Burton
    Apr 25 at 0:13






  • 7




    $begingroup$
    Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
    $endgroup$
    – the_fox
    Apr 25 at 0:14






  • 2




    $begingroup$
    @NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
    $endgroup$
    – amd
    Apr 25 at 1:37






  • 1




    $begingroup$
    @NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
    $endgroup$
    – amd
    Apr 25 at 3:32







  • 2




    $begingroup$
    If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
    $endgroup$
    – YawarRaza7349
    Apr 25 at 3:55













5












5








5


2



$begingroup$


I am practicing for a math contest and I encountered the following problem that I don't know how to solve:



For which value of $b$ is there only one intersection between the line $y = x + b$ and the parabola $y = x^2 + 5x + 3$?



How do I solve it?



Edit:
I made a mistake typing the problem. It should be $y = x^2 - 5x + 3$ instead of $y = x^2 + 5x + 3 $ the answer key says the answer is -6.










share|cite|improve this question











$endgroup$




I am practicing for a math contest and I encountered the following problem that I don't know how to solve:



For which value of $b$ is there only one intersection between the line $y = x + b$ and the parabola $y = x^2 + 5x + 3$?



How do I solve it?



Edit:
I made a mistake typing the problem. It should be $y = x^2 - 5x + 3$ instead of $y = x^2 + 5x + 3 $ the answer key says the answer is -6.







algebra-precalculus contest-math






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Apr 25 at 18:03







joeny

















asked Apr 25 at 0:10









joenyjoeny

754




754







  • 1




    $begingroup$
    Do you know how to find a derivative?
    $endgroup$
    – R. Burton
    Apr 25 at 0:13






  • 7




    $begingroup$
    Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
    $endgroup$
    – the_fox
    Apr 25 at 0:14






  • 2




    $begingroup$
    @NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
    $endgroup$
    – amd
    Apr 25 at 1:37






  • 1




    $begingroup$
    @NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
    $endgroup$
    – amd
    Apr 25 at 3:32







  • 2




    $begingroup$
    If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
    $endgroup$
    – YawarRaza7349
    Apr 25 at 3:55












  • 1




    $begingroup$
    Do you know how to find a derivative?
    $endgroup$
    – R. Burton
    Apr 25 at 0:13






  • 7




    $begingroup$
    Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
    $endgroup$
    – the_fox
    Apr 25 at 0:14






  • 2




    $begingroup$
    @NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
    $endgroup$
    – amd
    Apr 25 at 1:37






  • 1




    $begingroup$
    @NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
    $endgroup$
    – amd
    Apr 25 at 3:32







  • 2




    $begingroup$
    If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
    $endgroup$
    – YawarRaza7349
    Apr 25 at 3:55







1




1




$begingroup$
Do you know how to find a derivative?
$endgroup$
– R. Burton
Apr 25 at 0:13




$begingroup$
Do you know how to find a derivative?
$endgroup$
– R. Burton
Apr 25 at 0:13




7




7




$begingroup$
Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
$endgroup$
– the_fox
Apr 25 at 0:14




$begingroup$
Simply $x^2+5x+3=x+b$ must have only one solution, i.e. $x^2+4x+(3-b)=0$ should have zero discriminant.
$endgroup$
– the_fox
Apr 25 at 0:14




2




2




$begingroup$
@NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
$endgroup$
– amd
Apr 25 at 1:37




$begingroup$
@NoChance Your observation would be relevant if the line’s equation were of the form $y=b$. The line in the problem is not horizontal, though.
$endgroup$
– amd
Apr 25 at 1:37




1




1




$begingroup$
@NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
$endgroup$
– amd
Apr 25 at 3:32





$begingroup$
@NoChance If you’re going to to that route, then you want the one that has the same slope as the given line.
$endgroup$
– amd
Apr 25 at 3:32





2




2




$begingroup$
If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
$endgroup$
– YawarRaza7349
Apr 25 at 3:55




$begingroup$
If this problem is for a math contest, I think it's more likely the problem was written with a non-calculus solution in mind. (Also, the question is tagged algebra-precalculus.)
$endgroup$
– YawarRaza7349
Apr 25 at 3:55










3 Answers
3






active

oldest

votes


















26












$begingroup$

Hint:
$$x^2+5x+3=x+biff x^2+4x+3-b=0,$$ this quadratic equation should have exactly one solution therefore the discriminant $Delta=?$






share|cite|improve this answer









$endgroup$




















    3












    $begingroup$

    Note that you like the line $y=x+b$ to be tangent to the parabola. The slope of this line is $ m=1.$ Thus the derivative of your parabola should be the same as the slope of the tangent line. Find the point of the tangency and find the $b$ value so that the line passes through that point.






    share|cite|improve this answer









    $endgroup$




















      2












      $begingroup$

      The tangent to parabola has slope $y' = 2x+5$ which should be slope of line =1 at the point of contact. So point of contact is at x=-2. Substituting in parabola,we get y=-3. Now this point lies on line as well.






      share|cite|improve this answer









      $endgroup$













        Your Answer








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        3 Answers
        3






        active

        oldest

        votes








        3 Answers
        3






        active

        oldest

        votes









        active

        oldest

        votes






        active

        oldest

        votes









        26












        $begingroup$

        Hint:
        $$x^2+5x+3=x+biff x^2+4x+3-b=0,$$ this quadratic equation should have exactly one solution therefore the discriminant $Delta=?$






        share|cite|improve this answer









        $endgroup$

















          26












          $begingroup$

          Hint:
          $$x^2+5x+3=x+biff x^2+4x+3-b=0,$$ this quadratic equation should have exactly one solution therefore the discriminant $Delta=?$






          share|cite|improve this answer









          $endgroup$















            26












            26








            26





            $begingroup$

            Hint:
            $$x^2+5x+3=x+biff x^2+4x+3-b=0,$$ this quadratic equation should have exactly one solution therefore the discriminant $Delta=?$






            share|cite|improve this answer









            $endgroup$



            Hint:
            $$x^2+5x+3=x+biff x^2+4x+3-b=0,$$ this quadratic equation should have exactly one solution therefore the discriminant $Delta=?$







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Apr 25 at 0:14









            HAMIDINE SOUMAREHAMIDINE SOUMARE

            4,0431625




            4,0431625





















                3












                $begingroup$

                Note that you like the line $y=x+b$ to be tangent to the parabola. The slope of this line is $ m=1.$ Thus the derivative of your parabola should be the same as the slope of the tangent line. Find the point of the tangency and find the $b$ value so that the line passes through that point.






                share|cite|improve this answer









                $endgroup$

















                  3












                  $begingroup$

                  Note that you like the line $y=x+b$ to be tangent to the parabola. The slope of this line is $ m=1.$ Thus the derivative of your parabola should be the same as the slope of the tangent line. Find the point of the tangency and find the $b$ value so that the line passes through that point.






                  share|cite|improve this answer









                  $endgroup$















                    3












                    3








                    3





                    $begingroup$

                    Note that you like the line $y=x+b$ to be tangent to the parabola. The slope of this line is $ m=1.$ Thus the derivative of your parabola should be the same as the slope of the tangent line. Find the point of the tangency and find the $b$ value so that the line passes through that point.






                    share|cite|improve this answer









                    $endgroup$



                    Note that you like the line $y=x+b$ to be tangent to the parabola. The slope of this line is $ m=1.$ Thus the derivative of your parabola should be the same as the slope of the tangent line. Find the point of the tangency and find the $b$ value so that the line passes through that point.







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered Apr 25 at 0:21









                    Mohammad Riazi-KermaniMohammad Riazi-Kermani

                    42.4k42061




                    42.4k42061





















                        2












                        $begingroup$

                        The tangent to parabola has slope $y' = 2x+5$ which should be slope of line =1 at the point of contact. So point of contact is at x=-2. Substituting in parabola,we get y=-3. Now this point lies on line as well.






                        share|cite|improve this answer









                        $endgroup$

















                          2












                          $begingroup$

                          The tangent to parabola has slope $y' = 2x+5$ which should be slope of line =1 at the point of contact. So point of contact is at x=-2. Substituting in parabola,we get y=-3. Now this point lies on line as well.






                          share|cite|improve this answer









                          $endgroup$















                            2












                            2








                            2





                            $begingroup$

                            The tangent to parabola has slope $y' = 2x+5$ which should be slope of line =1 at the point of contact. So point of contact is at x=-2. Substituting in parabola,we get y=-3. Now this point lies on line as well.






                            share|cite|improve this answer









                            $endgroup$



                            The tangent to parabola has slope $y' = 2x+5$ which should be slope of line =1 at the point of contact. So point of contact is at x=-2. Substituting in parabola,we get y=-3. Now this point lies on line as well.







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered Apr 25 at 0:21









                            TojrahTojrah

                            87010




                            87010



























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