Question

1）已知a=-(-2)的平方2、b=-(-3)的三次方、c=-(-4的平方),则-[a-(b-c)]的值是多少?

2）化简并求值
xy-2{xy-[3x²y-(xy²+0.5xy)]+4x²y}，其中x=1，y=2

Answer 1

a=-4，b=27,c=16
所以原式=-a+b-c=4+27-16=15

xy-2{xy-[3x²y-(xy²+0.5xy)]+4x²y}
=xy-2xy+2[3x²y-(xy²+0.5xy)]-8x²y
=-xy+6x²y-2(xy²+0.5xy)-8x²y
=-xy-2x²y-2xy²-xy
=-2xy-2x²y-2xy²
=-4-4-8
=-16

Answer 2

a=-4，b=27,c=16
所以原式=-a+b-c=4+27-16=15

xy-2{xy-[3x²y-(xy²+0.5xy)]+4x²y}
=xy-2xy+2[3x²y-(xy²+0.5xy)]-8x²y
=-xy+6x²y-2(xy²+0.5xy)-8x²y
=-xy-2x²y-2xy²-xy
=-2xy-2x²y-2xy²
=-4-4-8
=-16

Answer 3

a=-4，b=27,c=-16
所以原式=-a+b-c=4+27+16=47

=xy-2xy+2[3x²y-(xy²+0.5xy)]-8x²y
=-xy+6x²y-2(xy²+0.5xy)-8x²y
=-xy-2x²y-2xy²-xy
=-2xy-2x²y-2xy²
=-4-4-8
=-16