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January 29, 2015

January 29, 2015

Posted by **-Untamed-** on Monday, October 31, 2011 at 6:40pm.

4x^2+23x+15

2x and 2x times to make a 4x. 5 and 3 times to make 15. And Im left with 10x and 6x, and they are supposed to add to make a 23x. But they are not:\ Ive even tried flipping them, but there's no point because the numbers are the same.

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 6:48pmtry

(x-5)(4x-3)

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 6:51pmNow to do that I solved the quadratic equation (google that)

I found for solutions

x = 5 and x = 6/8 which is 3/4

so

(x-5)(x-3/4) = 0 is solution

I can multiply both sides by 4 to get rid of the faction

(x-5)(4x-3) = 0

- Factoring Trinomials -
**-Untamed-**, Monday, October 31, 2011 at 6:52pmHow did you get that using the criss cross method?

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 6:54pmsolving for zeros with quadratic equation:

[ -23 +/- sqrt (529 - 240) ]/8

[-23+/-17]/8

-40/8 and -6/8

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 6:55pmI never heard of the criss cross method. I used the quadratic equation to solve for zeros of the quadratic expression.

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 6:58pm5 and 4 make 20

1 and 3 make 3

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 7:00pmDo it backwards from my solution and you will see :)

- Factoring Trinomials -
**-Untamed-**, Monday, October 31, 2011 at 7:02pmFor the criss cross method, Im supposed to find two numbers that multiply to get 4x^2. And those were 2x and 2x. Then, Im supposed to find two numbers that multiply to give me 15, which was either 15 and 1 or 3 and 5. I used both, by criss crossing 2x to 3 and 2x to 5. That gave me 10x and 6x which does not give me 23x, and same with using 15 and 1, that just gave me 28, -28, etc.

- Factoring Trinomials -
**-Untamed-**, Monday, October 31, 2011 at 7:07pmNevermind, I think I got it. Thanks for showing me the Quadratic way.

- Factoring Trinomials -
**Damon**, Monday, October 31, 2011 at 7:15pmBut 1 * 4 = 4 as well :)

- Factoring Trinomials -
**t**, Monday, December 19, 2011 at 5:32pmb-6b+8

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