已知A=x三次方+2y三次方-xy二次方,B=-y三次方+x三次方+2xy二次方,其中x=三分之一,y=2,求a-b的值

2025-04-25 00:03:11
推荐回答(2个)
回答1:

A-B=x³+2y³-xy²-(-y³+x³+2xy²)
=x³+2y³-xy²+y³-x³-2xy²
=3y³-3xy²
=3*2³-3*1/3*2²
=24-4
=20

回答2:

A-B=x³+2y³-xy²-(-y³+x³+2xy²)
=x³+2y³-xy²+y³-x³-2xy²
=3y³-3xy²
=3y²(y-x)
=3*2*2*(2-1/3)
=20