c = 169
square is (x + 13)^2
Explanation:
In the form:
ax^2+ bx +c
to complete the square a = 1 is required.
c = (b/2)^2
the square term is b/2
x^2 + 26x + c
a = 1 so we are okay to complete the square.
b = 26
c = (26/2)^2 = 13^2 = 169
finally to complete the square:
x^2 + 26x + 169 = (x+b/2)^2 = (x+13)^2
