Question

Resolver a expressão
Cx,2=15

Answer 1

Oi Bruna

C(x,2) = 15

C(x,2) = x!/(2!(x - 2)!) = 15

x!/(x - 2)! = 2*15 = 30

x*(x - 1)*(x - 2)!/(x - 2)! = 30

x² - x = 30

x² - x - 30 = 0

delta
d² = 1 + 120 = 121
d = 11

x = (1 + 11)/2 = 12/2 = 6