Answer Check - Find an equation of the tangent line

  • #1

Homework Statement


Find an equation of the tangent line to the curve y = 5x3 at the point

(-3,-135). Enter your equation in y = form.

Homework Equations




The Attempt at a Solution



Taking the derivative of the equation I get

y = 15x2, following that I plug in the x value of the given point:
y = 15(-3)2
and get
y = 135

Am I doing this correctly?
 

Answers and Replies

  • #2
quasar987
Science Advisor
Homework Helper
Gold Member
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18
First, you should write the derivative of y with a different symbol than "y". Conventional notations for the derivative are y' or dy/dx.

So you have found

y'(x) = 15x² ==> y'(-3)=135,

which is correct. But y'(3) represents the slope of the curve y(x) at the point (-3,-135). You are asked to find an equation for the line of slope 135 and passing through the point (-3,-135).
 

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