Help me factor 12a^2-147?

12a^2 - 147
= 3(4a^2 - 49)
= 3[(2a)^2 - 7^2]
= 3(2a + 7)(2a - 7)

1, 3, 7, 21, 49 and even 147 itself.

12a^2-147=3(4a^2-49)=3(2a+7)(2a-7)

12a^2-147
=12(a^2-147/12)
=12(a^2-(sqrt(147/12))^2)
=12(a+sqrt(147/12))(a-sqrt(147/12))---(1)
sqrt(147/12)=sqrt(49/4)=7/2
(1) can be rewritten as
=12(a+7/2)(a-7/2)
these are the factors

3 ( 4 a ² - 49 )

3 ( 2 a - 7 ) ( 2 a + 7 )

Looks like it's going to end up like this:

3(4a^2-49)

You just have to pull a 3 out of both terms.

use a calculator. or dont do it.