问题 选择题 已知反比例函数y=kx(k≠0)的图象过点P(2,12),则化简(x-1x)(y+1y)的结果是( )A.2x2B.2y2C.y2-x2D.x2-y2 答案 ∵反比例函数过点P,∴k=2×12=1,∴1x=y,1y=x,∴(x-1x)(y+1y)=(x-y)(x+y)=x2-y2.故选D.