SOLUTION: How do you solve this equation? 21x^2

SOLUTION: How do you solve this equation? 21x^2 - 6 = 15x ? thannkkkks . (:

Question 451839: How do you solve this equation?
21x^2 - 6 = 15x ?
thannkkkks . (:
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!

 

Hi,

21x^2 - 6 = 15x 

21x^2 - 15x-6 = 0

factoring

(7x +2)(3x -3) = 0  |  Note:SUM of the outside terms(-21x) and the inside terms(6x) = -15x

check the factoring using the FOIL method of multiplying binomials

F	First terms

O	Outside terms

I	Inside terms

L	Last terms

(7x +2)(3x -3) = 0 

(7x +2)= 0  x = -2/7

(3x -3) = 0  x = 1

 x = -2/7,1 

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