3a-4b=7
4b-3a+10
=-(3a-4b)+10
=-7+10
=3
|x+3|+（y-2)²=0
则x+3=0,y-2=0
x=-3,y=2
所以(3x-2y)分之xy
=5分之2
若|a+2|-3=6
|a+2|=9
a+2=±9
a=-11,a=7
1+3+5+7+……+49
=(1+49)+(3+47)+……+(23+27)+25
=50+50+……+50+25
=50×12+25
=625
1+3+7+……+2005
=(1+2005)+(3+2003)+……+(1001+1005)+1003
=2006+2006+……+2006+1003
=2006×501+1003
=1006009