CALCULUS
posted by ANONYMOUS on .
The expression dy/dx = x(cbrt(y)) gives the slope at any point on the graph of the function f(x) where f(2) = 8. B. Write an expression for f(x) in terms of x.
I can't figure out what to do with that cubed root; it keeps throwing me off.

dy/dx = x y^(1/3)
y^(1/3) dy = x dx
(3/2)y^(2/3) = (1/2)x^2 + c
when x = 2 , y = 8
(3/2)(4) = (1/2)(4) + c
c = 6  2 = 4
(3/2) y^(2/3) = (1/2) x^2 + 4
3 y^(2/3) = x^2 + 8
y^(2/3) = (1/3) x^2 + 8/3 
And then you could simplify it out to get y = (x^2/3 + 8/3)^(3/2). Thank you so much, I went back and ran (2, 8) through and it finally worked out, thanks!!!

your wrong

Strange, I did not write that.

All I did was solve for y so I could get the y by itself. I need to right the expression in terms of x, so I need to isolate y completely. In order to do this, I just applied the 2/3 root to both sides of the equation. Put in different terms, I could also say that it is to the 3/2 power. I worked it through with the initial condition f(2)=8, and it worked out. So, would you put your stamp of approval on this simplification.