# How does (a + b)^2 expand to (a^2 + 2ab + b^2) ?

#### DougB7430

##### New member
This is the problem that I was working on. Initially, I thought that the answer would be 1/a2 + b2

#### Subhotosh Khan

##### Super Moderator
Staff member
This is the problem that I was working on. Initially, I thought that the answer would be 1/a2 + b2
Do you under stand the following):

(a + b) * ( x + y) ..................using distributive law of multiplication, we get:

= a * (x + y) + b * (x + y) ..................using distributive law of multiplication again, we get:

= a*x + a*y + b*x + b*y

Follow the same steps - replace (x+y) by (a+b)

(a + b) * ( a + b)

= a*(a+b) + b*(a+b) .....................continue..........

#### Otis

##### Elite Member
This is the problem that I was working on. Initially, I thought that the answer would be 1/a2 + b2
Hi Doug. Subhotosh showed you the 'Double Distribution' method. There's another way to do the same thing; it's called the FOIL algorithm.

There's an explanation and example (with animations) at this site. Scroll about halfway down the page, to the subheading: 2 terms × 2 terms (binomial times binomial).