Homework Help: pre calculus

Posted by anon on Tuesday, December 20, 2011 at 9:40pm.

Solve the exponential equation Express you solutions in exact form only Please show your work
e^2x - 9e^x - 20 = 2

pre calculus - Reiny, Wednesday, December 21, 2011 at 9:13am
(e^x)^2 - 9e^x - 22 = 0
let y = e^x
y^2 - 9x - 22 = 0
(y-11)(y+2) = 0
y = 11 or y = -2
e^x = 11
x = ln 11

or

e^x = -2, no solution ( x = ln(-2) which is undefined)
pre calculus - anon, Wednesday, December 21, 2011 at 10:38am
Thank u!

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