Factor x-a in such a way that square root of x - square root of a is a factor

We want to factor the expression x - a, in such a way that we have one factor written as:

(√x - √a)

We will find that the factorized expression is:

(√x - √a)*(√x + √a)

Here we need to remember two things:

First, (√x)^2 = √(x^2) = x

also:

(x^2 - y^2) = (x + y)*(x - y)

Now, using the first property, we can rewrite our original expression as:

(x - a) = ( (√x)^2 - (√a)^2)

Now, using the second property, we can rewrite it as:

( (√x)^2 - (√a)^2) = (√x - √a)*(√x + √a)

Then we have:

(x - a) = (√x - √a)*(√x + √a)

Thus, we have factorized (x - a) in such a way that one of the factors is  equal to (√x - √a)

If you want to learn more, you can read:

72 is the answer to this problem