1) a. 3x + 6 = 3(x + 2)
b. A = 3(x + 2) + (x + 2)(x - 8)
= (x + 2)(3 + x - 8)
= (x + 2)(x - 5)
2) Factoriser
B = x² - 4 + (x - 1)(x + 2)
= (x - 2)(x + 2) + (x - 1)(x + 2)
= (x + 2)(x - 2 + x - 1)
= (x + 2)(2x - 3)
C = x² + 4x + (x + 1)(x + 4)
= x(x + 4) + (x + 1)(x + 4)
= (x + 4)(x + x + 1)
= (x + 4)(2x + 1)