determine r and is tangent to the graphic

Question

Be "R" a straight that passing for (−1, 1) and is tangent to the graphic of f (x) = x^3−x. To determined "R".

Answer 1

f(x) = x^3 - x

f'(x) = 3x^2 - 1

f'(-1) = 3(-1)^2 - 1

f'(-1) = 2

(y - 1) = 2(x + 1)