# Math Help - factorise

1. ## factorise

hi,

i nned to factorise this:

3x^2+5x-2=0

i know how to do these but im stuck on this one!

so if someone could lend some advise i would be very grateful!

thanks!

2. 5x = 6x-x

So,

$3x^2+5x-2$

$=3x^2+6x-x-2$

3. .

4. i don't understand, wouldn't you have 2 brackets one starting with 3x and the other x.

5. Originally Posted by andyboy179
i don't understand, wouldn't you have 2 brackets one starting with 3x and the other x.
Hi andyboy,

You are correct, but harish21 was showing you a neat little way of factoring besides the "guess and check" method.

Here is harish21's method.

First, multiply the leading coefficient times the constant: 3 times -2 = -6

Next, determine two numbers whose product is -6 and whose sum is the coefficient of the linear term which is +5.

You should easily see that -1 and 6 meet that criteria.

$3x^2+6x-1x-2$

Group the first two terms and factor out 3x.

$3x(x+2)-1x-2$

Group the last two terms and factor out -1.

$3x(x+2)-1(x+2)$

It's easy to see the two binomial factors are $(x+2)(3x-1)$

It takes a lot longer to explain it than it does to actually do it.