# Solving for X

• Apr 27th 2011, 08:02 PM
maca404
Solving for X
Sorry I am getting errors with latex so ill post in text form, I am getting an answer but I do not think it is right hopefully someone can tell me where I went wrong.

2 * (0.1)^(x+1) = 25

to clarify 2 times 0.1 to the power of x +1 equals 25

I got :

2 * x + 1 * log 0.1 = 25

2 * x * log 0.1 = 24

x * log 0.1 = 12

x = 12 / log 0.1

x = -12

Any input would be appreciated. Thanks
• Apr 27th 2011, 08:08 PM
pickslides
2 * (0.1)^(x+1) = 25

First divide both sides by 2.

(0.1)^(x+1) = 25/2

Now take logs of both sides
• Apr 27th 2011, 08:33 PM
Soroban
Hello, maca404!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

QUOTE

2*(0.1)^{x+1} .= .25

I got: .2 * x + 1 * log 0.1 .= .25
. . Wow ... This is really wrong!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We have: . . .2(0.1)^{x+1} .= .25

Divide by 2: . .(0.1)^{x+1} .= .12.5

Take logs: .log(0.1)^{x+1} .= .log(12.5)

. . . . . . . . . . (x+1)log(0.1) .= .log(12.5)

. . . . . . . . . . . . . . . . . . . . . . . log(12.5)
. . . . . . . . . . . . . . . . x + 1 .= .----------
. . . . . . . . . . . . . . . . . . . . . . . .log(0.1)

. . . . . . . . . . . . . . . . . . . . . . . log(12.5)
. . . . . . . . . . . . . . . . . . . x .= .---------- - 1
. . . . . . . . . . . . . . . . . . . . . . . .log(0.1)

• Apr 27th 2011, 10:44 PM
Wilmer
Tattoo this on your wrist: if a^p = b, then p = log(b) / log(a)