Calculus
posted by sh .
Find the intervals of increase and decrease for the following function:
y=x√((x1)^4)
y'=[(4x)^(1/2)]+(1/2)((4x)^(1/2))(1)(x)
y'=[(4x)^(1/2)](1/2x)((4x)^(1/2))
y'=((4x)^(1/2))[((4x)^1)1/2x]
I've already factored it, how come the zeros of the derivative aren't 4 and 0?

If I interpret your first line correctly it is
y = x√((x1)^4)
Isn't that
y = x(x1)^2 ??
then
y' x(2)(x1) + (x1)^2
= (x1)(2x  x + 1)
= (x1)(x+1)
= 0
so x = 1 or x = 1 are the zeros of the derivative.
I don't see where the (4x)'s in your second line come from, there wasn't even a 4x in the equation. 
Whoops, I combined 2 questions together.
The question is y=x√(4x). 
So what did you get for you factored derivative set equal to zero ?
Mine was (1/2)(4x)^(1/2)(3x8) = 0
x = 8/3