Factorization: 3d^2-147?

To factorize:
3d^2-147
= 3(d^2 - 49)
= 3(d + 7)(d - 7) Answer

To solve for d:
3d^2-147 = 0
3d^2 = 147
3d^2 / 3 = 147/3
d^2 = 49
d = + or -7 Answer

3 (d² - 49)
3 (d - 7)(d + 7)

I wish I knew what the cross method was !

a^2 - b^2 = (a + b)(a - b)

3d^2 - 147
= 3(d^2 - 49)
= 3(d^2 - 7^2)
= 3(d + 7)(d - 7)

3d^2-147
3(d^2-49)
3(d+7)(d-7)

Q. 3d^2 - 147
=> 3 ( d^2 - 49 )
=> 3 ( d - 7 )( d + 7 )

i don't know what you mean by the "cross method, but factor out a 3

3(d^2 - 49)

then the whole thing can be factored to

3(d+7)(d-7)

check by multiplying all the stuff

3(d^2 +7d - 7d - 49)

7d's cancel leaving

3(d^2 - 49)

= 3d^2 - 147

first
3(d^2 -49)
then
3(d+7)(d-7)

3d^2-147 = 3(d^2 - 49)= 3(d-7)(d+7)

3d^2-147
3(d^2-49)
3(x-7)(x+7)

3d^2-147 is like 3 * (d^2-49)
or
3 * (d - 7) * (d + 7)