(a^3+b^3)=(a+b)(a^2-ab+b^2) my question is why the -ab?

Question

anonymous · Answer

Are you asking why the term "-ab" is in the middle of the formula?

anonymous · Answer

Yes

anonymous · Answer

And not a positive ab

venomblast · Answer

it cant be ab because the 1st term "a^2" does not have a "b". you can only take out if all the term got something in common.

venomblast · Answer

it already factor in lowest term

anonymous · Answer

@Hollywood_chrissy 

Maybe it would help you see it to multiply out the stuff on the right side of the equation.

You end up with (a^2)(b) and (a)(b^2) terms, and by having "-ab", the signs on those terms alternate and ultimately all cancel out, leaving only the cubed terms.

It is similar to when you factor a difference of squares...
a^2 - b^2 = (a+b)(a-b)    <<-- the signs in the factored version cause the unwanted terms like "ab" to cancel out, leaving only the squared terms.

anonymous · Answer

Yeah, i just noticed that too.