解,得:漏贺
唯稿[-(y-2x)(y+2x)-4(x-2y)^2]/(2y)
==(4x^2-y^2-4(x-2y)^2)/(2y)
==(4x^2-y^2-4x^2+16xy-16y^2)/(2y)
==(16xy-17y^2)/(2y)
==(16x-17y)/2
把x,y带入(16x-17y)/2,得:
指搜孝 [16*1-17*(-2)]/2==(16+34)/2
==8+17
==25
原式=[(4x^2-y^2)-4(x-2y)^2]/2y=[4(x+x-2y)(x-x+2y)]/2y-y/2=8(x-y)-y/轮激2=8x-17y/2把x=1,y=-2代入得原式兄桐塌羡圆=8+17=25