(1)根据题意列得:(2x2-x+1)-(x2+6x-5)=2x2-x+1-x2-6x+5=x2-7x+6,
正确的算式应为:(x2-7x+6)-(x2+6x-5)=x2-7x+6-x2-6x+5=-13x+11;
(2)原式=x2-2xy+y2+4x2-y2-4x2-2xy=x2-4xy,
当x=-1,y=[1/4]时,原式=1-4×(-1)×[1/4]=1+1=2.
(1)根据题意列得:(2x2-x+1)-(x2+6x-5)=2x2-x+1-x2-6x+5=x2-7x+6,
正确的算式应为:(x2-7x+6)-(x2+6x-5)=x2-7x+6-x2-6x+5=-13x+11;
(2)原式=x2-2xy+y2+4x2-y2-4x2-2xy=x2-4xy,
当x=-1,y=[1/4]时,原式=1-4×(-1)×[1/4]=1+1=2.