# Exponentials and logarithims

• Oct 30th 2008, 01:30 PM
gamboo
Exponentials and logarithims
http://i75.photobucket.com/albums/i2...ooji/maths.jpg

I get as far as dy/dx= -3e^-3x +2, then making this equal to zero, then going blank (Headbang)
• Oct 30th 2008, 01:46 PM
mr fantastic
Quote:

Originally Posted by gamboo
http://i75.photobucket.com/albums/i2...ooji/maths.jpg

I get as far as dy/dx= -3e^-3x +2, then making this equal to zero, then going blank (Headbang)

$0 = -3e^{-3x} +2 \Rightarrow \frac{2}{3} = e^{-3x} \Rightarrow \ln \frac{2}{3} = -3x \Rightarrow x = -\frac{1}{3} \ln \frac{2}{3}$.

Substitute into $y = e^{-3x} + 2x$ and simplify to get the given value of y.