• Mar 24th 2009, 04:57 AM
TYTY
For example:
$
6x^2 +11x -35
$

I've been doing this by trial and error but it takes too long. I tried googling "factoring quadratics" but when it comes to examples like this, they just use the quadratic equation to find the values of x assuming the whole equation was equal to zero in the first place. I don't think this helps me.

I need the answer in the form (....)(....) and I don't think the answer on, for example,
Solving Quadratic Equations: Examples, does that
. What I need is the strategy to find this. I know I'm going to need +7. -5 or -7, +5 at the ends but from there I just have to try so many combinations.
• Mar 24th 2009, 05:18 AM
stapel
Try this lesson on factoring quadratics. (Wink)

(The posted link was for solving equations, rather than factoring expressions.)
• Mar 24th 2009, 05:21 AM
TYTY
Quote:

Originally Posted by stapel
Try this lesson on factoring quadratics. (Wink)

(The posted link was for solving equations, rather than factoring expressions.)

yes this looks exactly like what I am looking for (Talking)
• Mar 24th 2009, 05:24 AM
rtblue
There is a quadratic formula, to find the roots. Google Quadratic formula. I personally prefer factoring tho :D
• Mar 24th 2009, 05:49 AM
masters
Quote:

Originally Posted by TYTY
For example:
6x2 + 11x – 35

I've been doing this by trial and error but it takes too long. I tried googling "factoring quadratics" but when it comes to examples like this, they just use the quadratic equation to find the values of x assuming the whole equation was equal to zero in the first place. I don't think this helps me.

I need the answer in the form (....)(....) and I don't think the answer on, for example, Solving Quadratic Equations: Examples, does that. What I need is the strategy to find this. I know I'm going to need +7. -5 or -7, +5 at the ends but from there I just have to try so many combinations.

Hi TYTY,

Here's one strategy you might find helpful.

$6x^2+11x-35$

Multiply the leading coefficient (6) by your constant (-35) to get -210.

Next, try to come up with 2 factors that multiply to get -210 and sum to +11.

You may have to fiddle around a little to find them, but this one came to me right away. It's +21 and -10.

Replace the middle coefficient (-11) with these two numbers:

$6x^2+21x-10x-35$

Now, group the first two terms and the last 2 terms and factor out the greatest common factor for each.

$3x(2x+7)-5(2x+7)$

Use the distributive property to finish up.

$(3x-5)(2x+7)$
• Mar 24th 2009, 06:13 AM
TYTY
Quote:

Originally Posted by masters
Hi TYTY,

Here's one strategy you might find helpful.

$6x^2+11x-35$

Multiply the leading coefficient (6) by your constant (-35) to get -210.

Next, try to come up with 2 factors that multiply to get -210 and sum to +11.

You may have to fiddle around a little to find them, but this one came to me right away. It's +21 and -10.

Replace the middle coefficient (-11) with these two numbers:

$6x^2+21x-10x-35$

Now, group the first two terms and the last 2 terms and factor out the greatest common factor for each.

$3x(2x+7)-5(2x+7)$

Use the distributive property to finish up.

$(3x-5)(2x+7)$

Excellent explanation.