1)2x +3x(2次方)+x-2x(2次方)
=3x+x(2次方)
=x(3+x)

2)8x+4 over 2-(3x-2)
=8x+2-3x+2
=5x+4

3)5(a-1) over 2-4(a+1) over 3
= 3乘5(a-1)over2乘3-4乘2(a+1)over3乘2
=15(a-1)over6-8(a+1)over6
=15(a-1)-8(a+1)
=15a-15-8a-8
=7a-23