Verified answer

are you saying f(x) as in y = -2 or are you suggesting to substituting x for -2

Not sure if the radical goes over the whole problem but I'm bored so I'll do both.

f(x) = sqrt[(5-2x) - x/2]

-2 = sqrt[(5-2x) - x/2]

4 = (5-2x) - x/2

I think you can solve the rest from here....

f(x) = sqrt[(5-2x)] - x/2

-2 = sqrt[(5-2x)] - x/2

-2 + x/2 = sqrt[(5-2x)]

square both sides and combine

[(-4+x)/2]^2 = 5-2x

(16 - 8x + x^2)/4 = 5 - 2x

multiply both sides by four to eliminate the denominator on the right side of the equation

16 - 8x + x^2 = 20 -8x

I think you can take it from here....(use the quadratic formula)