Question

用乘法公式计算（1)(3a-b)(b+3a)-(2b+a)(-2b-a) (2)(-x-2y)(x+2y)

Answer 1

（1) (3a-b)(b+3a)-(2b+a)(-2b-a) =(3a-b)(3a+b)+(2b+a)²=9a²-b²+4b²+4ab+a²=8a²+4ab+3b².(2) (-x-2y)(x+2y)=-(x+2y)(x+2y)=-(x²+4xy+y²)= - x²-4xy-y²