SOLUTION: please find the equation of the tangent to the curve given by y= x^3 - 5x + 15 at the point where x= -1 I got the answer to be y= -2x +17 but im not sure if this is right. co

Question 330494: please find the equation of the tangent to the curve given by
y= x^3 - 5x + 15
at the point where x= -1
I got the answer to be
y= -2x +17
but im not sure if this is right.
could you show working if im incorrect please.thanks
Found 2 solutions by Jk22, Fombitz:
Answer by Jk22(389) (Show Source): You can put this solution on YOUR website!
Q : tangent to the curve given by
y= x^3 - 5x + 15
at the point where x= -1 ?

y(-1)=-1+5+15=19
y'(x)=3*x^2-5, y'(-1)=3-5=-2
let ytan(x)=ax+b
ytan(-1)=-a+b=19
ytan'(-1)=a=-2 => b=19+a=17
hence ytan(x)=-2x+17
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
The slope of the tangent line equals the value of the derivative at x=-1.

At

Use the point-slope form of a line,

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That's what I get too.
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