问题
解答题
先化简,再求值: ①(-
②[(a+b)(a-b)+(a-b)2+4a2(a+1)]÷a,其中b-3a-2a2=4. |
答案
①原式=
x2y2•1•[2x2y-xy2-2x2y+2xy2]1 9
=
x2y2•xy21 9
=
x3y41 9
当x=-
,y=2时,3 2
原式=
×(-1 9
)3×243 2
=
×(-1 9
)×2427 23
=-6;
②[(a+b)(a-b)+(a-b)2+4a2(a+1)]÷a
=[a2-b2+a2-2ab+b2+4a3+4a2]÷a
=[6a2-2ab+4a3]÷a
=6a-2b+4a2…
∵b-3a-2a2=4,
∴等式两边都除以-1得:3a-b+2a2=-4,
∴原式=6a-2b+4a2…
=2(3a-b+2a2)
=2×(-4)
=-8.