Question

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

Answer 1

When f(x)=x^2-1
and f(2a)=35 it means that: x=2a
{ x^2-1=35

so: (2a)^2-1=35
4(a^2)-1=35
4(a^2)=35+1
4(a^2)=36 /4
a^2=9
a=3

Answer 2

f(2a)=35
f(2a)=(2a)^2-1=35
(2a)^2-1=35
add 1 both sides
(2a)^2=36
sqrt both sides
2a=+/-6
divde 2
a=+/-3

a=3 or -3