What value is added to both sides of the equation x2 – 8x = –10 in order to solve by completing the square?

a. –8
b. 16
c. –4
d. 4
I think its a, am i right?

Question

What value is added to both sides of the equation x2 – 8x = –10 in order to solve by completing the square?

a.  –8
  b.  16
  c.  –4
  d.  4
I think its a, am i right?

mertsj · Answer

One half of 8 is 4 and 4 squared is 16 so add 16 to both sides.

anonymous · Answer

wait what

anonymous · Answer

what mertsj said, with exactly that reasoning

anonymous · Answer

forget the number on the right hand side, it is irrelevant

anonymous · Answer

you have 
$$x^2-\color{red}{8}x$$
$$\frac{8}{2}=4, 4^2=16$$ add 16 to both sides get 
$$(x-4)^2=-10+16=6$$

anonymous · Answer

you should think it in english exactly as mertsj wrote it
half of 8 is 4, 4 squared is 16

anonymous · Answer

oh i see, i guess i understand better with visual. Thanks a ton!

anonymous · Answer

$$x^2+12x=-5$$ half of 12 is 6, 6 squared is 36
$$(x+6)^2=-5+36$$ etc