If the cost of manufacturing x items is x^3 + 21x^2 + 110x + 20 , find the marginal cost at x = 100 and the actual cost of manufacturing the 100th item.

Question

If the cost of manufacturing x items is x^3 + 21x^2 +  110x + 20  , find the marginal cost at x = 100 and the actual cost of manufacturing the 100th item.

anonymous · Answer

I did it but i got wrong 

C(x) = x^3 + 21x^2 + 110x + 20
F’9x) = 3x^2 + 42 _ 110
100^3 + 21(100)^2 + 110(100) + 20 = 1221020
99^3 + 21(99)^2 + 110(99) + 20 = 1187030
c(100) – c(99) = 1033990
f’(x) = 3x^2 + 42 + 110 = 24310
actual cost : 1033990
marginal cost: 34310

anonymous · Answer

My teacher told me to re evaluate c(100) - c(99)

anonymous · Answer

@tcarroll010  can u help?

anonymous · Answer

c(100) is correct, so is c(99)
c(100) - c(99) = 1221020 - 1187030 = 34020 - 30 = 33990

anonymous · Answer

ok