How to solve Quadratics by Factoring
Favorites|Homepage
Subscriptions | sitemap
HOME > Mathematics > How to solve Quadratics by Factoring

How to solve Quadratics by Factoring

[From: ] [author: ] [Date: 11-10-29] [Hit: ]
k = -1, 8-5k^2+43k-40=8k.You have to first get all the numbers on one side, so that they all equal 0.So subtract 8k from each side:5k^2+35k-40=0.You know if you multiply 2 numbers together an the answer is 0,......
>.< This is embarrassing, but how do you solve Quadratics by Factoring? (I'm a little stuck)
5k^2+43k-40=8k.
Please list the steps.

Thank you very much.

-
5k^2 + 43k - 40 = 8k
5k^2 - 35k - 40 = 0
k^2 - 7k - 8 = 0

two numbers that multiply to equal -8, add to equal -7
1, -8

(k - 8)(k + 1) = 0
k = -1, 8

-
5k^2+43k-40=8k.
You have to first get all the numbers on one side, so that they all equal 0.
So subtract 8k from each side: 5k^2+35k-40=0.
You know if you multiply 2 numbers together an the answer is 0, then one of them must equal 0, right? If you have ab = 0, then either a=0 or b=0.
So you have to separate 5k^2+35k-40 into two parts that multiply together: (.....)(.....)=0
You look at the 5k^2 and the 5 must be 5 x 1.
You look at the - 40, and there are lots o possible numbers that multiply to make 40. 4x10, 2x20, etc., and one of them has to be negative to make -40.
So you play around with the numbers a lot, guessing here and there, knowing that since the +35 is positive, then a bigger number will be multiplied by 5, and you end up with:
(5k -5 )(1k + 8) =0

Now, either 5k -5 = 0, or 1k + 8 = 0,

Solve each of those for k and you'll get your two answers.
1
keywords: solve,to,Factoring,How,by,Quadratics,How to solve Quadratics by Factoring
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .