Posted by **Anonymous** on Wednesday, December 26, 2012 at 3:53pm.

Solve by completing the square.

5x^2+10x-7=0

My answer: x= -1+ or - 2sqrt.of 10 all over 5

- Algebra 2 .. -
**Reiny**, Wednesday, December 26, 2012 at 3:55pm
divide by 5

x^2 + 2x + ... = 7 + ...

x^2 + 2x + 1= 7 + 1

(x+1)^2 = 8

x+1 = ± √8 = ± 2√2

x = -1 ± 2√2

- oops - Algebra 2 .. -
**Reiny**, Wednesday, December 26, 2012 at 4:16pm
forgot to divide the 7 by 5

x^2 + 2x + 1 = 7/5 + 1 = 12/5

(x+1)^2 = ±√12/√5 = ± √60/5 = ± 2√15/5

x = -1 ± 2√15/5

x = (-5 ± 2√15)/5

- Algebra 2 .. -
**Anonymous**, Wednesday, December 26, 2012 at 7:21pm
I do not get it. Here let me show my work.

5x^2+10x-7=0

5(x^2+2x+1)-7-1

5(x+1)^2-8=0

5(x+1)^2=8

(x+1)^2=+/- sqrt of 8/5

(x+1)=+/- 2sqrt of 2 over sqrt of 5

(x+1)=+/- 2sqrt of 10 over 5

x= -1+/- 2sqrt of 10 all over 5

- Algebra 2 .. -
**Anonymous**, Wednesday, December 26, 2012 at 7:27pm
WAIT NEVER MIND.....

MY FINAL ANSWER IS X=-1+/-2 SQRT OF 15 ALL OVER 5

- Algebra 2 .. -
**Anonymous**, Wednesday, December 26, 2012 at 7:29pm
But why is your answer x=-5+/- 2sqrt of 15 all over 5?

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