we need to Derive the following expressions:

P=(1+1/(1-L)^2)/2

1 y=1/x

2 y=1/x^2;

3 移动x的对称轴

备注: 这两项数值相等: (1-x)^2 --- (x-1)^2

4 y=1+1/(1-x)^2 -->将y轴向上提升1

5 y=(1+1/(1-x)^2)/2-->将y轴数值压缩一半

函数推进