At a bowling alley, shoe rentals cost $3 and each game costs $4. The average cost c (in dollars) of bowling n games is given by c=4n+3n. Find how many games you must bowl for the average cost to fall to $4.75 by (a) solving an equation, and (b) using the inverse of a function.

Respuesta :

Answer: 0.67857

Explanation:

a ) Given the equation we simply group terms and solve n for c =4.75:

[tex]c = 4n+3n\\c = n(4+3)\\c/7 =n=>4.75/7 = 0.678\\\\[/tex]

b) We first check if the function is invertible (let n1 and n2 be any values for the function c = 4n+3n) So we have to prove ([tex]f(n_{1}) = f(n_{2})[/tex] => [tex]n_{1} = n_{2}[/tex])

so we have[tex]f(n_{1})= 7n_{1}\\f(n_{2}) = 7n_{2}\\  ( f(n_{1}) =f(n_{2}) ) =(7n_{1}=7n_{2}) = (n_{1}=n_{2})[/tex]

finally [tex]n_{1} = n_{2}[/tex]. This is a check you always do to find if a function is invertible (it has to be injective).

Now solving the problem we just replace c with n and n with c:

[tex]n = 4c + 3c = c(4+3) = 7c => n/7 = c[/tex]

where n = 4.75

finally:

[tex]c = 4.75/7 = 0.67857[/tex]

that is the number of games you need.

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