If f(x) = 3 − 7x, find f ^−1(−25).

Question

If f(x) = 3 − 7x, find f ⁻¹(−25).

Answer 1

f(x) = 3 - 7x is linear, so we can solve for x to do it more easily. Then we insert -25 for y, and that gives us f^-1(-25).

y = 3 - 7x

y - 3 = -7x

-(y-3)/7 = x

-(-25 - 3) / 7 = x

-(-28) / 7 = x

4 = x