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ForumsDiscussion Forum → Derivative help
Derivative help
2007-10-29, 8:35 PM #1
All knowing Massassians, how would I derive y = x^(x+1) ? Do I have to take log base x on both sides?

2007-10-29, 8:52 PM #2
exponential rule
2007-10-29, 9:22 PM #3
y' = x^x(ln(x)x + x + 1)
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2007-10-30, 10:54 AM #4
Take the natural log (ln) of both sides of the equation.

ln(y) = ln(x^(x+1)) = (x+1) ln(x)

Then do d/dx of both sides.

By the chain rule on the right:

d(ln(y))/dx = (1/y) * dy/dx

By the product rule on the left:

d((x+1)ln(x))/dx = ln(x) + (x+1)/x


Then putting the two sides back together:

(1/y)*dy/dx = ln(x) + (x+1)/x

or

dy/dx = y * (ln(x) + (x+1)/x)

But we have y explicitly defined in terms of x, so:

dy/dx = x^(x+1) * (ln(x) + (x+1)/x)

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