Find the linear approximation to f(x) = sqrt(1-4x) at x=-2 I keep getting (-2/3)*x +(13/3) as the answer, but it is wrong?
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Originally Posted by Velvet Love Find the linear approximation to f(x) = sqrt(1-4x) at x=-2 I keep getting (-2/3)*x +(13/3) as the answer, but it is wrong? check your arithmetic ... I get $\displaystyle y = -\frac{2}{3}x + \frac{5}{3}$
yes you took the derivative correctly, but it looks like something went wrong when you brought 3 over from the left hand side, or maybe when you multiplied through by $\displaystyle -\frac{2}{3}$
Can you show me the steps? I do everything by the book, and i still get that answer.
Originally Posted by Velvet Love Can you show me the steps? I do everything by the book, and i still get that answer. The equation of the tangent line is $\displaystyle y-b=m(x-a)$ m is your derivative evaluated at a, which you did correctly, so what went wrong was solving for y after that, it's an error in your arithmetic $\displaystyle y-3=-\frac{2}{3}(x-(-2))$
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