Find an equation of the line tangent to the curve at the point (7,-5)

I tried to solve it but can't get the right answer, can you help me check it out?

Derivative

The equation is

But the right answer is

Where is my error?

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- March 9th 2013, 09:40 PMshihoFind an equation of the line tangent
Find an equation of the line tangent to the curve at the point (7,-5)

I tried to solve it but can't get the right answer, can you help me check it out?

Derivative

The equation is

But the right answer is

Where is my error? - March 9th 2013, 10:40 PMCesc1Re: Find an equation of the line tangent
If I'm not mistaken your answer is correct.

- March 10th 2013, 01:32 AMhollywoodRe: Find an equation of the line tangent
I agree with Cesc1 - your answer is correct.

- Hollywood - March 10th 2013, 04:31 AMILikeSerenaRe: Find an equation of the line tangent
- March 10th 2013, 09:08 AMshihoRe: Find an equation of the line tangent
ah thanks for your explanation

maybe this time the answer paper is wrong xD