Finding Tangent Line to a Curve at a Given Point

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SUMMARY

The discussion focuses on determining the values of a and b for which the line 3x + y = b is tangent to the curve y = ax^3 at the point where x = 5. The key steps involve finding the slope of the tangent line, which is -3, and equating it to the derivative of the curve at x = 5. The correct derivative calculation is crucial, as an earlier miscalculation led to confusion regarding the correct answer for online homework submissions.

PREREQUISITES
  • Understanding of calculus concepts, specifically derivatives
  • Familiarity with polynomial functions, particularly cubic functions
  • Knowledge of linear equations and their slopes
  • Ability to solve algebraic equations
NEXT STEPS
  • Study the process of finding derivatives of polynomial functions
  • Learn how to determine the equation of a tangent line at a given point
  • Explore the relationship between the slope of a tangent line and the derivative of a function
  • Practice solving problems involving tangents to curves with varying degrees
USEFUL FOR

Students studying calculus, particularly those learning about tangent lines and derivatives, as well as educators looking for examples of real-world applications of these concepts.

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Homework Statement



For what values of a and b is the line 3x+y=b tangent to the curve y=ax^3 when x=5 ?


The Attempt at a Solution


I believe i would need to find the equation of the tangent to y=ax^3 when x=5 then that should be equal to -3x+b=y if I am not mistaken but I am not sure what to do from here to solve for a and b.

Any leads in the right direction or insight if this is the entirely wrong approach would be greatly appreciated!
 
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I believe i would need to find the equation of the tangent to y=ax^3 when x=5 then that should be equal to -3x+b=y if I am not mistaken
Well, yes, that's just a restatement of the problem! You know that the slope of y= -3x+ b is -3. What connection is there between the slope of a tangent line and the function itself?
 
thank you for the quick reply hallsofivy. I had -0.04 instead of -3/75 giving me the wrong answer for the online homework webpage which was confusing me. After using -3/75 instead it counts it as correct :(
 

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