Find the linear approximation L(x) to the function f(x)=2x^(-2) at the point, x=4 and use it to estimate the value of f(39/10).

I already found L(x:
L(x):(1/8)-(x-4)/16+0((x-4)^2)

How do you find f(39/10)?

f(39/10) = 2(39/10)^-2 = 2(10/39)^2 = ...

See how that compares to your estimate.

L(x) might be more clearly written as

y = -1/16 x + 3/8