先化简后求值:3(-2x-x²y)-12x²y-(6y-9x²y+1).其中x与y互为相反数.
问题描述:
先化简后求值:3(-2x-x²y)-12x²y-(6y-9x²y+1).其中x与y互为相反数.
答
只能化简,求不出值
答
-6x-3x²y-12x²y-6y+9x²y-1
-6x-6y-1-6x²y
x与y互为相反数
x=-y
6y-6y-1-6y^3
-1-6y^3
答
3(-2x-x²y)-12x²y-(6y-9x²y+1).
=﹣6x-3x²y-12x²y-6y+9x²y-1
=﹣6x-6y-6x²y-1
=﹣6﹙x+y﹚-6x²y-1
=﹣6x²y-1.