Question

F(x) = x^-1, x=.9. Use linear approximation to estimate answer

Answer 1

L(x) = f'(a)(x - a)
f(x) = x^(-1), f'(x) = -x^(-2)
Let a = 1, f'(a) = -(1)^(-2) = -1
L(0.9) = f'(1)(0.9 - 1) = -1(-0.1) = 0.1

Therefore, linear approximation of f(x) = x^(-1) for x = 0.9 is 0.1