SOLUTION: Solve 3^x+1=100. okay i'm getting 3.192 But my answer choices are different so can someone help me? My answer choices are in the link below please copy and paste the link belo

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: Solve 3^x+1=100. okay i'm getting 3.192 But my answer choices are different so can someone help me? My answer choices are in the link below please copy and paste the link belo      Log On


   

Question 1019596: Solve 3^x+1=100.
okay i'm getting 3.192 But my answer choices are different so can someone help me?
My answer choices are in the link below please copy and paste the link below to see! Thanks
link ; http://prntscr.com/a2w2c0
Found 3 solutions by josmiceli, richard1234, MathTherapy:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+x%5E3+%2B+1+=+100+
+x%5E3+=+99+
I'll take log base 10 of both sides
+3%2Alog%28x%29+=+log%2899%29%0D%0A%7B%7B%7B+3%2Alog%28x%29+=+1.9956+
+log%28x%29+=+.6652+
+x+=+10%5E.6652+
+x+=+4.6259+
---------------
check:
+x%5E3+%2B+1+=+100+
+4.6259%5E3+%2B+1+=+100+
+98.992+%2B+1+=+100+
+99.992+=+100+
Error due to rounding off

Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Given , take the log base 3 of both sides to get



It's not immediate from the answer choices, but you can obtain the correct answer (which is actually A) by rewriting the value for x as (using change-of-base). , so the expression is equivalent to

, or choice A.


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
Solve 3^x+1=100.
okay i'm getting 3.192 But my answer choices are different so can someone help me?
My answer choices are in the link below please copy and paste the link below to see! Thanks
link ; http://prntscr.com/a2w2c0 
Your answer is correct, but is an approximation of the value of x.

If you look at the answer choices, you can see that x needs to be an EXACT value.



3%5E%28x+%2B+1%29+=+100

log+%28%283%5E%28x+%2B+1%29%29%29+=+log+%28%28100%29%29 ------- Taking the log of both sides

%28x+%2B+1%29+%2A+log+%28%283%29%29+=+2 ------ log 100 = 2

x+%2B+1+=+2%2Flog+%28%283%29%29

x+=+%282%2Flog+%283%29%29+-+1

highlight%28highlight_green%28highlight%28x+=+%282+-+log+%283%29%29%2Flog+%283%29%29%29%29 ------- Multiplying right-side by LCD, log 3