Transform the polynomial into a perfect square trinomial to solve
x^2-4x=5
a){-5,13}
b){-7,11}
c){1,7}
d){-1,5}

X² - 4x = 5 ⇒ x² - 4x - 5 = 0

x² ⇒ x * x
-5 ⇒ -5 * 1
-4 ⇒ -5 + 1

(x + 1)(x - 5) = x(x-5) + 1(x-5) 
x² - 5x + 1x - 5 = x² - 4x - 5

x + 1 = 0
x  = -1

x - 5 = 0
x = 5

y = x² - 4x - 5
y = -1² - 4(-1) - 5
y = 1 + 4 - 5
y = 5 - 5
y = 0

y = x² - 4x - 5
y = 5² - 4(5) - 5
y = 25 - 20 - 5
y = 0

When i did the math i got 11 cm