The most important thing for physics is that you are comfortable with your math skills. For Physics B, this should be algebra but for Physics C you need to know calculus. The actual physics can all be learned in the class itself.
Don't remove the parentheses until after you've foiled it out or you're going to lose a negative sign.
Foiling 1-[(cos(x)+sin(x))(cos(x)-sin(x))], we get
1-(cos^2(x)-cos(x)sin(x)+cos(x)sin(x)-sin^2(x)). Two of the terms cancel, yielding:
1-(cos^2(x)-sin^2(x))
=1-cos^2(x)+sin^2(x)
Now try using...
Many schools come out with undergraduate admissions on April 1st, there's still a good chance that you will get in somewhere, so don't give up hope so easily.
Continuing from Dick's hint:
(x-y)^2 ≥ 0 (Trivial inequality)
x^2-2xy+y^2 ≥ 0
And adding 2xy to both sides, we get:
x^2+y^2 ≥ 2xy as desired.
And if you're up for it, try proving the two variable case of the AM-GM inequality from here (it's pretty simple).
As someone said earlier, without a strong foundation in algebra, calculus will be difficult, especially at this level. The calculus can sometimes get hard enough as is, without the tricky minutiae of algebra!
Work is spelled with a lower case "w", not Work; as this is a physics forum, I would assume most of the posters here know that when talking about work, the physics definition is implied.