Could someone please explain this?
Solve by completing the square: x² + 10x = 18
a)–11.56, 1.56 b)11.56, 1.56 c)–11.56, –1.56 d)11.56, –1.56

Question

Could someone please explain this? 
Solve by completing the square: x² + 10x = 18  
a)–11.56, 1.56 b)11.56, 1.56 c)–11.56, –1.56 d)11.56, –1.56

amorfide · Answer

completing the square:
you will do (x+b/2)²-(b/2)²=18
add -(b/2)² to both sides 
now square root both sides to get x+b/2  on the left hand side
this will give x+b/2= plus or minus root of whatever is on the right
-b/2 on both sides
x=__________

anonymous · Answer

I did that...I didn't get any of the answers listed!