This is LaTeX code:

[latex]
v-v_1 = 50 \implies v = 50+v_1 \\\\
250:10=(50+v_1)^2:v_1^2 \\
25 v_1^2 = 2500 + 100v_1 + v_1^2 \\
24v_1^2-100v_1 - 2500 = 0 \\
6v_1^2 - 25v_1 - 625 = 0 \implies v_{1_1} = -\frac{100}{12},\,v_{1_2} = 12.5\,cm
[/latex]