Factor Trinomials, can't find factors to equal sum.

[bobisaka]

3y(2y^2+6y-20)

After finding GCF, i cannot get factors of 20 to equal to the sum of the middle monomial 6, what method am i suppose to use now?

Can i use trial and error method?

 

[Harry_the_cat]

You need to find 2 numbers which multiply to ac = 2 x -20 = -40 (not 20) and add up to b=6.

 

[bobisaka]

It appears, I am not up to that method in the textbook..

Is it necessary to learn all the different types of methods?

 

[lev888]

It appears, I am not up to that method in the textbook..

Is it necessary to learn all the different types of methods?

There are other methods but doing what post #2 suggests is pretty straightforward.

 

[Cubist]

3y(2y^2+6y-20)

After finding GCF...

you didn't find the GCF correctly.
2, 6, and -20 are all even and can therefore be further divided by 2

 

[Harry_the_cat]

Yes, Cubist is correct. If you factored out 6y rather than 3y, you will be able to factorise the trinomial using the method you have already learnt.