# Need someone to check this Answer.

• Mar 22nd 2009, 04:26 PM
Kenlen83
http://img5.imageshack.us/img5/9369/letssee.png

I know i mess up somewhere on the signs.

• Mar 22nd 2009, 10:21 PM
Quote:

Originally Posted by Kenlen83
http://img5.imageshack.us/img5/9369/letssee.png

I know i mess up somewhere on the signs.

x^ 3 +1/8

= x^3 + (1/2)^3

= (x+1)(x^2 + 1/4 - x/2 )

-------------------------------

Formula used is
a^3 +b^3

= (a+b)(a^2 + b^2 - ab)
• Mar 23rd 2009, 05:11 AM
stapel
Quote:

Originally Posted by Kenlen83
I know i mess up somewhere on the signs.

There's a mnemonic for keeping track of the signs. The factoring formulas are:

. . . . . $\left(a^3\, -\, b^3\right)\, =\, (a\, -\, b)\left(a^2\, +\, ab\, +\, b^2\right)$

. . . . . $\left(a^3\, +\, b^3\right)\, =\, (a\, +\, b)(\left(a^2\, -\, ab\, +\, b^2\right)$

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:

. . . . . $(a\, \mbox{ S }\, b)\left(a^2\, \mbox{ O }\, ab\, \mbox{ AP }\, b^2\right)$

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".

(Wink)