计算:(1/3x+y)(1/3x-y)(1/9x2+y2).
问题描述:
计算:(
x+y)(1 3
x-y)(1 3
x2+y2). 1 9
答
原式=[(
x)2-y2](1 3
x2+y2)1 9
=(
x2-y2)(1 9
x2+y2)1 9
=(
x2)2-(y2)21 9
=
x4-y4.1 81