Posted by Anonymous on .
Solve by completing the square.
5x^2+10x7=0
My answer: x= 1+ or  2sqrt.of 10 all over 5

Algebra 2 .. 
Reiny,
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,
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,
I do not get it. Here let me show my work.
5x^2+10x7=0
5(x^2+2x+1)71
5(x+1)^28=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,
WAIT NEVER MIND.....
MY FINAL ANSWER IS X=1+/2 SQRT OF 15 ALL OVER 5 
Algebra 2 .. 
Anonymous,
But why is your answer x=5+/ 2sqrt of 15 all over 5?