6x squared + 15x -9

Question

6x² + 15x -9

 

Answer 1

Hi Susan;

6x² + 15x -9

3(2x²+5x-3)

We can set this equal to zero...

3(2x²+5x-3)=0

The parenthetical equation must equal zero.  Therefore, we can eliminate the 3...

2x²+5x-3=0

For the FOIL...

FIRST must be (2x)(x)=2x²

OUTER and INNER must add-up to 5x.

LAST must be (3)(1) or (1)(3) and either number must be negative to produce -3.

(2x-1)(x+3)

Let's FOIL...

FIRST...(2x)(x)=2x²

OUTER...(2x)(3)=6x

INNER...(-1)(x)=-1x=-x

LAST...(-1)(3)=-3

2x²+6x-x-3

2x²+5x-3

(2x-1)(x+3)=0

Either or both parenthetical equations must equal zero...

2x-1=0

2x=1

x=1/2

x+3=0

x=-3

Answer 2

You want to solve:

 

   6X^2 + 15X - 9 =0

 

    3 ( 2X^2 + 5X - 3 )

 

     3 ( 2X^2 + 6X - X -3 ) =0

 

       3 [ 2X( X +3 ) - ( X +3 ) ] =0

  

        3 [ ( X +3 ) ( 2X -1) ] =0

 

           X +3 = 0   X = -3    , 2X -1 = 0  X = 1/2