Hi everyone,
Just a reminder that we do not have class today. I’ll be posting a new lesson on Thursday.
Best,
Prof. Reitz
2020 Spring – MAT 1375 Precalculus – Reitz
A City Tech OpenLab Course Site
Hi everyone,
Just a reminder that we do not have class today. I’ll be posting a new lesson on Thursday.
Best,
Prof. Reitz
Professor! This is Suim Kim.
I am trying to solve Exponential Functions – Equations: Problem 7 on webwork
(1.31)x=28
but I am still struggling to solve it. It is a bit hard to not have any decimals. How do can I make it in an exact form with no approximations? I tried to multiply number 100 to each section but what I got is x= (log 2800)/(log 131) which is not an answer.
I hope our class can talk about it!
Thank you and I hope you stay healthy and safe.
[latexpage]
Hi Suim! Sure, I can help. You started with:
$(1.31)^x=28$
Take the log of both sides:
$\log (1.31^x)=\log 28$
and move the exponent to the front:
$x \log 1.31 = \log 28$
Unfortunately, we can’t get rid of the decimal by multiplying both sides by 100 — because the decimal is buried inside the $\log$, and multiplying $100 \log 1.31$ is not the same as $\log 131$.
Instead, we will use the fact that 1.31 = 131/100, and substitute this in the left side:
$x \log (131/100) = \log 28$
Now get the $x$ by itself to obtain your answer.
Hope this helps – let me know if you’re still stuck.
All the best,
Prof. Reitz