The solutions to f(x) = 64 is x = 7 and x = –7.
Solution:
Given data:
and
To find the solutions when f(x) = 64.
Both are equations of f(x), so equate the given equations, we get

Subtract 15 from both sides of the equation.


49 can be written as 7².

Taking square root on both sides of the equation, we get
x = ±7
The solutions to f(x) = 64 is x = 7 and x = –7.