（3a³-ab+7)-(5ab-4a²+7)
=3a³-ab+7-5ab+4a²-7
=3a³+4a²-6ab
=24+16-4
=36
（x+2）²+ 2y+3的绝对值=0
所以x+2=0,2y+3=0
x=-2,y=-3/2
6（ x²-3X)-2(X-2X²Y)-2X(-10X)
=6X²-18X-2X+4X²Y+20X²
=26X²-20X+4X²Y
=104+40-24
=120
2(X²Y+3XY²)-[-2(X²Y-1)+XY²]
=2X²Y+6XY²+2X²Y-2-XY²
=4X²Y+5XY²-2
=4-5-2
=-3