If you meant to solve for x...
The rule of law of the square root of constants is taking the nearest divisible number which has a square root of an integer. In this case, 50 is divisible by 25. Hence sqrt of 50 is 5 sqrt 2. The sqrt of a variable applies the multiplication rule. x^6 is raised to 0.5 equal to x^3. Hence the answer is 5 x3 sqrt 2.
I find it best to switch everything exponents when taking derivatives.
F(x) = 7/x
Same as..
F(x) = 7x^-1
Take derivative..
F'(x) = -7x^-2
Plug in x = 1
F'(1) = -7(1)^-2
F'(1) = -7