Question

How do you factor completely `a^2 - 121b^2`?

Answer 1

`color(blue)((a+11b)(a-11b)`

Explanation:

`a^2−121b^2`
This expression can be rewritten as `(a)^2−(11b)^2`

Now, as per the below property,
`color(blue)(x^2-y^2=(x+y)(x-y)`, we can rewrite the expression as:

`(a)^2−(11b)^2=color(blue)((a+11b)(a-11b)`
(Here, `x=a,y=11b` )

So the factorised form of the expression is:
`=color(blue)((a+11b)(a-11b)`