问题
解答题
已知:a+b=-5,2a-b=-1.求ab(a+b2)-b2(ab-a)+2a(a-b2).
答案
∵a+b=-5,2a-b=-1,
∴a=-2,b=-3,
∴ab(a+b2)-b2(ab-a)+2a(a-b2)
=a2b+ab3-ab3+ab2+2a2-2ab2
=a2b-ab2+2a2
=(-2)2×(-3)-(-2)(-3)2+2×(-2)2
=-12+18+8
=14.
已知:a+b=-5,2a-b=-1.求ab(a+b2)-b2(ab-a)+2a(a-b2).
∵a+b=-5,2a-b=-1,
∴a=-2,b=-3,
∴ab(a+b2)-b2(ab-a)+2a(a-b2)
=a2b+ab3-ab3+ab2+2a2-2ab2
=a2b-ab2+2a2
=(-2)2×(-3)-(-2)(-3)2+2×(-2)2
=-12+18+8
=14.