Question

(3a-2b)(3a+3b) so this is foil but i always get messed up on it does anyone now how to do it

Answer 1

Explanation:

`\text{Use FOIL}\ (a+b)(c+d)=ac+ad+bc+bd:\\\\(3a-2b)(3a+3b)\\\\=(3a)(3a)+(3a)(3b)+(-2b)(3a)+(-2b)(3b)\\\\=9a^2+9ab-6ab-6b^2\qquad\text{combine like terms}\\\\=9a^2+3ab-6b^2`

Answer 2

9a^2 + 3ab - 6b^2

Explanation:

(3a-2b)(3a+3b)

First term of each grouping is 3a and 3a.

Multiply those you get 9a^2.

Outer term of each grouping is 3a and 3b.

Multiply those you get 9ab.

Inner term of each grouping is -2b and 3a.

Multiply those you get -6ab.

Last term of each grouping is -2b and 3b.

Multiply those you get -6b^2.

Add up all your products from above.

9a^2+9ab+-6ab+-6b^2

There are like terms here. The 9ab+-6ab which is 3ab.

So you can write your expression now as:

9a^2 + 3ab +-6b^2

9a^2 + 3ab - 6b^2