Question

Find the equation of the tangent to the graph at the indicated point.
f(x) = x2 − 4; a = 5
y=?
I had the answer of 25x -124, but that's wrong :( help please.

Answer 1

If x = 5, then substiute to find y, you get y = 21

Slope = derivative of f(x) = f'(x) = 2x

so the slope is 2x and at x = 5, the slope is 2(5) = 10

Equation of tangent line is y - 21 = 10(x - 5)
or, y - 21 = 10x - 50
or y = 10x - 29.