(1)原式=4x-4-2x2-2-2x2+x=-4x2+5x-6,当x=-3时,原式=-4×9+5×(-3)-6=-57;(2)原式=4a2-3a-2a2-a+1+2-a2+4a=a2+3,当a=2时,原式=4+3=7;(3)原式=5x2-3y2-7xy+2y2-5x2=-y2-7xy,当x=1,y=-2时,原式=-4-7×(-2)=10.