1.化简:
原式=4(x+1)^2-7(x^2-1)+3(x-1)^2
=4(x+1)^2-7(x^2-1)+3(x^2-1)
=4(x+1)^2-4(x^2-1)
=4x^2+8x+4-4x^2+4
=8x+8
当x=-2时,原式=8×(-2)+8
=-8
2.化简:
原式=(2x-5y^2-(5y+2x)^2
=(5y-2x)^2-(5y+2x)^2
=(5y-2x+5y+2x)(5y-2x-5y-2x)
=10y×(-4x)
=-40xy
当x=2011,y=-1/2011时,原式=-40×2011×-1/2011
=40
第三题题目再发你下,是不是:(a+b)(a-b)+a(2b-a)?