k = m−ym+1\sqrt{\frac{m-y}{m+1}}m+1m−y
k2^{2}2 = m−ym+1\;\frac{m-y}{m+1}m+1m−y
k2^{2}2m + k2^{2}2 = m - y
k2^{2}2 + y = m - k2^{2}2m
k2+y1−k2\;\frac{k^2+y}{1-k^2}1−k2k2+y = m 1−k21−k2\;\frac{1-k^2}{1-k^2}1−k21−k2
m = y+k21−k2\;\frac{y+k^2}{1-k^2}1−k2y+k2
