Find the factors of the following quadratic expressions.

Let x = a + b

7(a + b)² + 8(a + b) + 1 = 7x² + 8x + 1
7(a + b)² + 8(a + b) + 1 = (7x + 1)(x + 1)

Substitute x = a + b back

7(a + b)² + 8(a + b) + 1 = (7(a+b) + 1)((a+b) + 1)
7(a + b)² + 8(a + b) + 1 = (7a + 7b + 1)(a + b + 1)


(7a + 7b + 1)(a + b + 1)

The last one hope it works