NEED HELP ASAP !
Factor 6x^3+5x^2-18x-15

Question

NEED HELP ASAP !
Factor 6x^3+5x^2-18x-15

roadjester · Answer

This type of problem is mostly trial and error. What you want to focus on is the first and last term.

You have a $\large6x^3$  and a -15. From that you want to cross-multiply the terms until one gets you 5 and one gets you -18.

roadjester · Answer

Now, $\large +5x^2$ can only be generated with the 5 coming from the 15.

roadjester · Answer

That tells you that you're going to be using 3 and 5 in your constants with one being positive and one negative.

anonymous · Answer

http://www.wolframalpha.com/input/?i=factor+6x^3%2B5x^2-18x-15

roadjester · Answer

Ok, fine just give the answer away. @eliassaab  =(

anonymous · Answer

People should start using wolframalpha for this kind of questions and try to figure out themselves how wolframalpha got the answer.

anonymous · Answer

Thank you

anonymous · Answer

YW

roadjester · Answer

Fine, just pretend like I don't exist. =(

anonymous · Answer

Here how you do it by hand
$$
 6x^3+5x^2-18x-15= 6x^3-18x+5x^2-15=\
6x( x^2 -3) + 5(x^2-3)=(6x +5)(x^2-3)=(6x+5)( x- \sqrt 3)(x+\sqrt 3)
$$