一道因式分解题，求过程和解。

通分：=(100x^4+20x²y-y²）／100
=｛-（10x²）²+2·（10x²y）-y²｝／100
=-｛（10x²）²-2·（10x²y）+y²｝/100
=-（10x²-y）²/100 =-（x²-y/10）²
注：x^4指x的四次方
还清楚吧！！

[(1/5)x^2y]-x^4-[(y^2)/100]
=(x^2y/5)-x^4-(y^2/100)
=-[-(x^2y/5)+x^4+(y^2/100)]
=-[x^2-(y/10)]^2
=-(x^2-y/10)^2

[（1/5）·x^2·y]-（x^4)-[(y^2)/100]
=-[(x^2)^2-x^2y/5+(y/10)^2]
=-(x^2-y/10)^2