c^2 + 11c = 12
c^2 + 2[11/2] c = 12
[c + 11/2] ^2 - [11/2]^2 = 12
[c +11/2]^2 = 12 +[11/2]^2
[c +11/2]^2 = 12 + 121/4
[c +11/2]^2 =[48+121]/4
[c +11/2]^2 = 169/4 ----> This is the resulting equation
Solving it you get:
c + 11/2 = +/- √(169/4)
c + 11/2 = +/- 13/2
c = 13/2 - 11/2 =2/2 = 1 and
c = -13/2 - 11/2 = - 24/2 = -12
