问题
解答题
化简求值: (1)[(2x2y)2-(-2xy)3-xy2(-4xy2)2]÷8x2y3,其中x=-1,y=-2. (2)(m2-6mn+9n2)÷(m-3n)-(4m2-9n2)÷(2m-3n),其中m=-3,n=-
|
答案
(1)原式=[(4x4y2)•(-8x3y3)-xy2(16x2y4)]÷8x2y3,
=[(-32x7y5)-(16x3y6)]÷8x2y3,
=-4x5y2-2xy3,
把x=-1,y=-2代入,原式=4×4-2×8=0;
(2)原式=(m-3n)2÷(m-3n)-(2m-3n)(2m+3n)÷(2m-3n)
=(m-3n)-(2m+3n)
=-m-6n,
把m=-3,n=-
代入,原式=3+6×1 3
=5.1 3