X=kgt2
2u(1+k)
make k the subject
(top 2 meaning sqaured)

Do you mean this?


x = \frac {kgt^2} {2u(1+k)}


If so, you can multiply through by 2u(1+k) to get:


2u(1+k)x = kgt^2 \\
2ux+2ukx = kgt^2 \\
2ux = kgt^2 - 2ukx = k(gt^2 - 2ux) \\
k = \frac {2ux} {gt^2 - 2ux}