Question

Given the quadratic function f(x) = x2 – 18x + 81, find a value of x such that f(x) = 16.

Answer 1

Just plug in 16 for f(x) in the first equation. Then solve for x by factoring.

Answer 2

actually you might need the quadratic formula for this one.

Answer 3

let

\[x^2 - 18x + 81 = 16\]

subtract 16 from both sides

then \[x^2 - 18x + 65 = 0\]

factorize to find the solutions

\[(x - 13)(x-5) = 0\]