Question

el costo C en dolares por operar cierta maquina cortadora de concreto esta realacionado con el numero n de minutos que la maquina trabaja mendiante la funcion c(n)=2..2n^2-66n+655

Answer 1

C(n) = 2.2n^2 - 66n + 655 

The "n" value of the vertex can be found using the formula: 
n = -b / 2a 

where: 
a = 2.2 
b = -66 
c = 655 

n = -b / 2a 
n = -(-66) / 2*(2.2) 
n = 66 / 4.4 
n = 15 

Now plug (n = 15) back into the equation and solve for C(n): 
C(n) = 2.2(15)^2 - 66(15) + 655? 
C(n) = 2.2*(225) - 990 + 655 
C(n) = 495 - 335 
C(n) = 160 

Running the machine for 15 minutes gives the lowest cost, 
which is equal to $160 (I'm assuming dollars $ here). 

I tried looking for a website that explains this little trick, 
but all of them are cluttered and confusing for most folks. 

Good luck in your studies, 
~ Mitch ~