How fast does a certain nebula recede if the hydrogen line `lambda = 434 nm` in its spectrum is displaced by `130 nm` toward longer wavelengths?

Explanation

From the previous problem using
`k = (2pi)/(lambda)`
we get `lambda' = lambda sqrt((1+v//c)/(1-v//c))`
Thus `(1+(v)/(c ))/(1-v//c) = (lambda'^(2))/(lambda^(2))`
or `v//c = (lambda'^(2)-lambda^(2))/(lambda'^(2) + lambda^(2)) = (564^(2)-434^(2))/(564^(2)+434^(2)) = 0.256`