Question

c(n)=-1/5n^2 8n 100

Answer 1

$ Ola Eduarda

-n²/5 + 8n + 100 = 0

-n² + 40n + 500 = 0

delta
d² = 1600 + 2000 = 3600
d = 60

n1 = (-40 + 60)/-2 = -10
n2 = (-40 - 60)/-2 = 50 

pronto