# Math Help - easy function question

1. ## easy function question

a function is defined as follows: f:[-2,a] = R where f(x) = (x-1)^2 -4

if f(a) = 12 then find the value of a

if anyone could help me with this it would be very much appreciated

2. Originally Posted by gbooker
a function is defined as follows: f:[-2,a] = R where f(x) = (x-1)^2 -4

if f(a) = 12 then find the value of a

if anyone could help me with this it would be very much appreciated
hi

f(a)=(a-1)^2-4

12=(a-1)^2-4

(a-1)^2=16

$a-1=\pm 4$

a=5 or a=-3

but check its domain , [-2,a]

-3 is outside the domain , so a=5 .

3. thanks for a lot for your help