Question

21x^2+46x+24
I think the answer is
(7x+6)(3x+4)
If I am not correct why?

Answer 1

For the x^2 part it should factor into 7x * 3x or 21x * x

Let's try 7x * 3x:

(7x ) (3x )

For the 24 part there are a bunch of possibilities: 1 * 24, 2 * 12, 3 * 8, 4 * 6

Let's try 3 * 8

(7x 3) (3x 8)

7*8 = 56, 3*3 = 9

Can't make 46 out of 56 and 9. . .

(7x 8) (3x 3)

7*3 = 21, 8*3 = 24

Can't make 46 out of 21 and 24. . .

Let's try 4 and 6

(7x 4) (3x 6)

7*6 = 42, 4*3 = 12

Can't make 46 out of 42 and 12

(7x 6) (3x 4)

7*4 = 28, 6*3 = 18

We can make 46 out of 28 and 18, so let's try this:

(7x + 6) (3x + 4)

Expand that out and we get. . .

your right