Answer:
-13
Step-by-step explanation:
2x²+26x+156=0
x²+13x+78=0
x²+13x=-78
x²+13x+169/4=-143/4
(x+13/2)²=-143/4
x+13/2=(i√143)/2 or x+13/2=-(i√143)/2
x=(i√143)/2-13/2 or x=-(i√143)/2-13/2
(i√143)/2-13/2+(-(i√143)/2)-13/2=(i√143-13-i√143-13)/2=-26/2=-13
