Question

determine o valor de n nas equaçoes: n!/(n-2)!=56

Answer 1

n!/(n-2)! = 56

n(n - 1)(n - 2)!/(n - 2)! = 56

n(n - 1) = 56
n² - n - 56 = 0

∆ = b² - 4ac
∆ = (- 1)² - 4.1.(- 56)
∆ = 1 + 224
∆ = 225

x = -b±√∆ /2a
x = -(- 1)±√225 /2.1
x = 1±15 /2

x' = 1+15 /2
x' = 16/2
x' = 8

x" = 1 - 15 /2
x" = - 14/2
x" = - 7

R.: n' = 8 ; n" = - 7