1627190 there's your answer.
F(x)=3x2-11
f(5)=6-11
5f=-5
5f/5=-5/5
f=-1
The question is a bit ambiguous: you may mean

or

Anyway, in both cases, the domain of a function involving a square root is found by imposing the content of the root to be greateer than or equal to zero. So, in the first case you have

In the second case, you have

Hi there!

2x - 4y = 9
Begin by isolating the y variable by moving 2x to the right-hand side of the equation. (Subtract 2x from both sides):
2x - 2x - 4y = 9 - 2x
-4y = 9 - 2x
Further isolate by dividing both sides by -4:
-4y / (-4) = (9 - 2x) / (-4)
y = -9/4 - 2x/(-4)
Simplify further:
y = -9/4 + 1/2x
y = 1/2x - 9/4
The "b" value is the y-intercept, therefore:
x = 0 at y = -9/4