1.3x的二次方+my-8-(-nx的平方+2y+7)
=(3+n)x²+(m-2)y-15
∵不含有x,y
∴3+n=0
m-2=0
∴m=2
n=-3
∴n的m次方+m的n次方=9+1/8=73/8
2.3ab-[2a-(2ab-2b)+3]
=3ab-2a+(2ab-2b)-3
=3ab-2a+2ab-2b-3
=-2(a+b)+5ab-3
=-2 x 4 + 5 x 3 -3
=-8+15-3
=4
3.(x+2)²+丨y+1丨=0
x+2=0 x=-2
y+1=0 y=-1
5xy²-{2x²y-[3xy²-(4xy²-2x²y)}
=5xy²-[2x²y-(3xy²-4xy²+2x²y)]
=5xy²-(2x²y+xy²-2x²y)
=5xy²-xy²
=4xy²
=4*(-2)*(-1)²
=-8
4.(x²+ax-2y+7)-(bx²-2x+9y-1)
=(1-b)x²+(a+2)x-11y+8
根据题意得
1-b=0,a+2=0
∴a=-2,b=1
5.能
原数【AB】= 10A + B
新数【BA】= 10B + A
和 = 10A+ B + 10B + A = 11A + 11B = 11(A + B)
含因数11,必能被11整除.
6.