X² - 12X + 36 = 0
Por Factorizacion
Podemos poner el - 12X como : - 12X = - 6X - 6X
X² - 12X + 36 = X² - 6X - 6X + 36
X² - 6X - 6X + 36 = (X² - 6X) - (6X - 36)
(X² - 6X) - (6X - 36) = X(X - 6) - 6(X - 6)
X(X - 6) - 6(X - 6) = (X - 6)(X - 6)
X² - 12X + 36 = (X - 6)(X - 6)
Ahora por formula general.
X² - 12X + 36 = 0
Donde : a = 1 ; b = - 12 ; c = 36
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B-b%5Cpm%20%5Csqrt%7Bb%5E2-4ac%7D%7D%7B2a%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B-%28-12%29%5Cpm%20%5Csqrt%7B%28-12%29%5E2-4%281%29%2836%29%7D%7D%7B2%281%29%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B12%5Cpm%20%5Csqrt%7B144-144%7D%7D%7B2%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B12%5Cpm%20%5Csqrt%7B0%7D%7D%7B2%7D" />
X = 12 / 2
X = 6
Solucion X = 6 ó
X² - 12X + 36 = (X - 6)(X - 6).