计算:(1)(-7x³y-3b²)(7x³y-3b²);(2)(3x+y-2)(3x-y+2).

问题描述:

计算:(1)(-7x³y-3b²)(7x³y-3b²);(2)(3x+y-2)(3x-y+2).

:(1)(-7x³y-3b²)(7x³y-3b²)
=-(7x³y+3b²)(7x³y-3b²)
=-(49x的6次方-9b的4次方)
=-49x的6次方+9b的4次方
(2)(3x+y-2)(3x-y+2).
=[3x+(y-2)][3x-(y-2)]
=9x²-(y-2)²
=9x²-y²+4y-4