SOLUTION: Please help me understand this. Thanks! 1/(4x + 2) - x/3 = -21/(10x + 5)

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Question 544158: Please help me understand this. Thanks!
1/(4x + 2) - x/3 = -21/(10x + 5)

Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!
- =
Factoring the denominators will help
- =
:
get rid of the some of the denominators, multiply by 30, results:
- 10x =
- 10x =
:
Multiply by (2x+1) and you have
15 - 10x(2x+1) = -126
-20x^2 - 10x = -126 - 15
-20x^2 - 10x = -141
:
Get rid of all those negatives, mult by -1
20x^2 + 10x = +141
20x^2 + 10x - 141 = 0
Solve this quadratic equation using the quadratic formula
I got: x = 2.417 and x = -2.917
these look like unlikely solutions, however, I check them both out in the original problem and got equality.

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