f(x)=x2−1That 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=4a2−1Now, we know that f(2a)=35so we can find the value of a:f(2a)=(2a)2−1=4a2−1=354a2−1+1=35+14a2=36a2=9a=±3
