1.
∵ (x＋2)2＋|y＋1|=0,∴ x＋2=0,y＋1=0,∴ x=－2,y=－1.
而 5xy2－{2x2y－[3xy2－(4xy2－2x2y)]}
=5xy2－{2x2y－[3xy2－4xy2＋2x2y]}
=5xy2－(2x2y＋xy2－2x2y)
=4xy2
當(dāng) x=－2,y=－1時(shí),原式=－8.
2.
|m+n-2|+(mn+3)^2=0
m+2=0,且mn+3=0
m=-2,n=3/2
2（ m+n）-2[mn+(m+n)]-3[2(m+n)-3m+n]
=-1-2(-3-1/2)-3(-1+6+3/2)
=6-15-9/2
=-27/2
3.
3倍的m²-mn=15加上2倍的mn-n²=-6,得3m²-mn-2n²=33
4.
1-6,2-5,3-4分布在每個(gè)對(duì)面即可
比如說(shuō)一個(gè)面是1,那么它的對(duì)面就是6,依次類推,即可滿足要求