Question

explain the steps......

Answer 1

See the coefficient of x. It is

$\frac{a}{a + b} + \frac{a + b}{b}$

It has been broken into two terms and product of the terms is 1 which is the constant term. (That's what we need when we factorise quadratic equation)

So if we write the constant term as product of the those terms, then we can take common(and factorise) easily.

So 1 is written as the product of the two terms which are coefficient of x.