I know i mess up somewhere on the signs.
There's a mnemonic for keeping track of the signs. The factoring formulas are:
. . . . .$\displaystyle \left(a^3\, -\, b^3\right)\, =\, (a\, -\, b)\left(a^2\, +\, ab\, +\, b^2\right)$
. . . . .$\displaystyle \left(a^3\, +\, b^3\right)\, =\, (a\, +\, b)(\left(a^2\, -\, ab\, +\, b^2\right)$
You've noticed that the terms inside the formula are always the same; it's only the signs that differ. Use "SOAP" to keep track of the signs:
Take the sign of the sum or difference of cubes that you're needing to factor. Then look at the two parentheses that you need to fill in:
. . . . .$\displaystyle (a\, \mbox{ S }\, b)\left(a^2\, \mbox{ O }\, ab\, \mbox{ AP }\, b^2\right)$
The letters stand for "the Same sign as what you're factoring", "the Opposite sign from what you're factoring", and "Always use a Plus sign here".