已知3(x+2)的平方和2乘x-y+1的绝对值互为相反数,求5x的平方y-﹛2x的平方y-[3xy的平方-(4xy的平方
已知3(x+2)的平方和2乘x-y+1的绝对值互为相反数,求5x的平方y-﹛2x的平方y-[3xy的平方-(4xy的平方-2x平方y]﹜
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∵3(x+2)²和|2(x-y+1)|互为相反数
即3(x+2)²=-2(x-y+1)|
∴x+2=0
x-y+1=0
∴x=-2,y=-1
5x²y-{2x²y-[3xy²-(4xy²-2x²y)]}
=5x²y-[2x²y-(3xy²-4xy²+2x²y)]
=5x²y-(2x²y-3xy²+4xy²-2x²y)
=5x²y-2x²y+3xy²-4xy²+2x²y
=(5-2+2)x²y+(3-4)xy²
=5x²y-xy²
=xy(5x-y)
=(-2)*(-1)*[5*(-2)-(-1)]
=2*(-10+1)
=2*(-9)
=-18
即3(x+2)²=-2(x-y+1)|
∴x+2=0
x-y+1=0
∴x=-2,y=-1
5x²y-{2x²y-[3xy²-(4xy²-2x²y)]}
=5x²y-[2x²y-(3xy²-4xy²+2x²y)]
=5x²y-(2x²y-3xy²+4xy²-2x²y)
=5x²y-2x²y+3xy²-4xy²+2x²y
=(5-2+2)x²y+(3-4)xy²
=5x²y-xy²
=xy(5x-y)
=(-2)*(-1)*[5*(-2)-(-1)]
=2*(-10+1)
=2*(-9)
=-18
1年前 追问
4
结果是一样的，把开头地方变一下就可以了 ∵3(x+2)²和2|(x-y+1)|互为相反数 即3(x+2)²=-2|(x-y+1)| ∴x+2=0 x-y+1=0 ∴x=-2，y=-1 有疑问请追问，满意请采纳
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