Factor 5 - 4x-12x^2

Question

Select the correct choice below.

(a) 5 - 4x-12x^2=?

(b) The trinomial is not factorable.

 

Answer 1

First re write the trinomial in descending order:

-12x^2-4x+5=0

Then factor out a -1:

-(12x^2+4x-5)=0

Write all possible factors for 12 and all possible factors of 5 to see all possibilities:

12:                    5:

1 x 12.              1 x 5

2 x 6

3 x 4

remember that:

(ax + n)(bx + m)

amx and bnx must add up to our middle term which in this case is 4x.

the only possible combination that works is:

(2x - 1)(6x + 5)

 

so completely factored our answer is:

-(2x - 1)(6x +  5)

 

hope this helps