Answer:
x^2+8x+4=0
(x+8/2)^2-(4^2)=-4
(x+4)^2-16=-4
(x+4)^2=-4+16
(x+4)^2=12
(x+4)=±√12
x=-4±√12
Explanation:
let's see with the equation ax^2+bx+c
and completing square equation is (x+b/2)^2-(b/2)^2+c
according to the question a=1,b=8 and c=4
by completing the square, x will lose its square and b will get divided by 2
so 8 divided by two is 4 that's why (x+4) and the bracket is square so (x+4)^2
4 which got from b will continue the equation with -(4^2) that results in -16
c=4 will go to other side and be -4
add 16 on both sides, -16 from left side will disappear and -4+16=12 in right side
multiply root on both sides
root from left side will disappear and 12 from left side will be ±√12
subtract -4 on both sides