Question

using the identity b-7 ka square

Answer 1

Heya !!

We know that,
(a-b)² = a²-2ab+b²

So, (b-7)²
=> b²-14b+49
=> b²-7b-7b+49
=> b(b-7) -7(b-7)
=> (b-7) (b-7)
=> b = 7