Answer:
5
Step-by-step explanation:
x² - 4x = 5
x² - 4x - 5 = 0
the solution of a quadratic equation is
x = (-b ± sqrt(b² - 4ac))/(2a)
a = 1
b = -4
c = -5
x = (4 ± sqrt(16 + 20))/2 = (4 ± sqrt(36))/2
x1 = (4 + 6)/2 = 5
x2 = (4 - 6)/2 = -1
since we are looking only for a positive number, x=5 is the answer.
