Find dy

kggirl

New member
Joined
Oct 5, 2005
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43
if y = x^2/1+x^2, find dy

my answer is 2x/2x dx which equals to 1dx


is this correct?
 
Hello, kggirl!

Sheesh . . . neither of you ever heard of the Quotient Rule ??

If \(\displaystyle y\:=\:\frac{x^2}{1\,+\,x^2}\), find \(\displaystyle dy\).
Differentiate: .\(\displaystyle \L\frac{dy}{dx}\:=\:\frac{(1\,+\,x^2)\cdot2x\,-\,x^2\cdot2x}{(1\,+\,x^2)^2}\:=\:\frac{2x\,+\,2x^3\,-\,2x^3}{(1\,+\,x^2)^2}\:=\:\frac{2x}{(1\,+\,x^2)^2}\)

Therefore: .\(\displaystyle \L dy\;=\;\frac{2x}{(1\,+\,x^2)^2}\,dx\)
 
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