Posted by michelle on .
y= u+3/u1 u=x^1/3 find dy/dx at x=8

Math please help urgent ! 
Damon,
dy/dx = dy/du du/dx
du/dx = (1/3)x^(2/3)
dy/du = [(u1)(u+3)]/(u1)^2
= [(x^(1/3)1)(x^(1/3)+3)/(x^(1/3)1)^2
= 4 / (x^(2/3) 2x^(1/3)+1)
so
dy/du * du/dx
=(4/3)(x^(2/3)) /(x^(2/3) 2x^(1/3)+1)
= 4/3(x^4/32x +x^(2/3)) 
Math please help urgent ! 
Damon,
luckily 8^(1/3) = 2 :)