Why is the square root of f(x)= √ x - 4, when x=4, equal to f(-2) and not f(0)?

Question

If you give x the value of 4 and 4-4=0 isn't the square root 0?

Is there an order to follow?

Thanks

Answer 1

It depends on the grouping. If the function is

f(x) = √(x - 4),

then

f(4) = √(4 - 4) = 0

But if the function is

f(x) = √x - 4,

then

f(4) = √4 - 4 = 2 - 4 = -2 (ignoring the negative square root)

Did the original problem have x-4 inside the square root, or just x inside the square root? It makes a big difference. By the way, it cannot be f(-2) either way, because you would be taking the square root of a negative number.