（1）-2（1\3x-3\2y)^2
=-2(1/9x²-xy+9/4y²)
=-2/9x²+2xy-9/2y²
(2)(x\2+5)^2-(x\2-5)^2
=(x/2+5-x/2+5)(x/2+5+x/2-5)
=10*2x/2
=10x解关于x的方程：(x+1\4)^2-(x-1\4)(x+1\4)=1\4(x+1\4)^2-(x-1\4)(x+1\4)=1\4(x+1/4)(x+1/4-x+1/4)=1/4(x+1/4)*1/2=1/4x+1/4=1/2x=1/2-1/4∴x=1/4