Cos(2x) = cos^2(x) - sin^2(x) - cos(x)
but sin^2(x) = 1 - cos^2(x)
cos(2x) - cos(x) = cos^2(x) - (1 - cos^2(x) ) - cos(x)
cos(2x) - cos(x) = cos^2(x) - 1 + cos^2(x) - cos(x)
cos(2x) - cos(x) = 2cos^2(x) - 1 - cos(x)
cos(2x) - cos(x) = (2cos(x) + 1)(cos(x) - 1)
I think this is what you have asked for.
Well, just by looking at the beginning of the problem, Jamelia had made the common mistake of thinking that

(<span>8.4852...)
</span>is equal to

(12)
If you want to estimate a square root like 72, simply find squares that would fit around the number you are looking to find, in our case, 72.
So 9*9 is 81, which is too high and 8*8 is 64, which is too low. So you know that somewhere between those numbers is what your root of 72 is!
Add 2 to both sides and x will equal 2
Answer:
-7/45
Step-by-step explanation:
First, find the lowest common denominator for 9 and 15. It's 45. Make both fractions over 45 by multiplying the top and bottom by the same number.

Since 15*3=45, multiply the top by 3 also. Since 9*5=45, multiply the top by 5 also.

Combine the fractions
Answer in lowest terms