To solve this for an equation that you can graph, you need to isolate the y variable. In order to do this, follow the order of operations for solving equation to get the equation.
2y^2 = x + 4 ----> divide both sides by 2
y^2 = 
----> take the square root of both sides
y = 
Now you have the equation solved for the y variable and can graph it.
Inverse variation is of the form y=k/x or if you prefer yx=k.
z=6.3 bar I assume you mean 6.33333333 forever
10z-z=63.3333...-6.3333
9z=57
z=57/9 (exact)
Now back to the problem...
xz=k, we are told x=3 and we have shown z=57/9 so we can solve for k, the constant of variation
k=3(57/9)=19
So our equation is:
xz=19, now we wish to know what z is when x=8 so
8z=19 divide both sides by 8
z=19/8
z=2.375 (exact, no rounding necessary)
