SOLUTION: I am in college algebra online and we have a study sheet of problems which we need to know how to solve one similar. The one I am having trouble with is (1+r)^4=3.6 I had started

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Question 475234: I am in college algebra online and we have a study sheet of problems which we need to know how to solve one similar. The one I am having trouble with is (1+r)^4=3.6 I had started by factoring but I was lost at what to do after I factored it out. I have r^4+4r^3+6r^2+4r+1=3.6 then subtracted 1 to get r^4+4r^3+6r^2+4r=2.6 now I am stuck. Thank you in advanced.
Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
(1+r)^4=3.6
1 + r = 3.6^(1/4)
r = 3.6^(1/4) - 1

r =~ 0.3774493

Answer by Edwin McCravy(20056) (Show Source):
You can put this solution on YOUR website!

You used the word "factoring" wrong. You said "I started by factoring".
But what you did was exactly the opposite of factoring. The left side
of the equation was ALREADY factored. What you did was "un-factor" it by
multiplying it out. But you shouldn't have done that.

Don't multiply that out. Instead take the root of both sides
with the same index as the exponent of the left side. That is,
take the 4th root of both sides. Now since 4 is even we must
get both the positive as well as the negative 4th root, so we
have this

The fourth root and the fourth power cancel on the left and we have
just

Solve for r:

We have two solutions, one using the + and one using the -.
Using the + :
which you can approximate with
a calculator as

Using the + :
which you can approximate with
a calculator as

Edwin