If f (x) = x2 - 1, and f (2a) = 35, then what could be the value of a?

f (x) = x2 - 1 That means to find the value of the function at any value of x, we square x and subtract 1. If x=2a, we square 2a and subtract 1: f (2a) = (2a) 2 - 1=4 a2 - 1 Now, we know that f (2a) = 35 so we can find the value of a: f (2a) = (2a) 2 - 1=4 a2 - 1=35 4 a2 - 1+1=35+1 4 a2 = 36 a2 = 9 a=±3