Question

eavalute the following using the identity (x+a)(x+b)=x^2 + (a+b)x+ab: 28×33​

Answer 1

Answer:

$let \\ 28 = 30 - 2 \\ 33 = 30 + 3 \\ so \: \: x = 30 \\ a = - 2 \: \: \: \: b = 3 \\ 28 \times 33 \\ = (30 - 2)(30 + 3) \\ = {(30)}^{2} + ( - 2 + 3)30 + ( - 2 \times 3) \\ = 900 + 30 - 6 \\ = 900 + 24 = 924$

Answer 2

23.45-76 56:234:78 68 is the answer