f(x) = -7x² + 32x + 240
f(0)=240
Answer for 240: The 240 is the revenue at the regular price, a $0 increase. It comes from 60 tacos at $4 a pop.
When we add $1 to the price we sell 53 tacos, 7 fewer.
Our revenue is 5*53 = 265
That matches f(1):
f(1) = -7 + 32 + 240 = 265
Let's see how to figure out f(x),
f(0)=4(60)=240
f(1)=5(60-7) = 265
f(2) = 6(60-2(7)) = 276
So in general,
f(n) = (n+4)(60 - 7n)
f(n) = 60n - 7n² - 28n + 240
f(n) = -7n² + 32n + 240
We see the 32n comes from 60n, which is the amount of additional money if we still sold 60 tacos at the new price, less 28n, which is the amount of money we didn't get at the original price because we raised the price.
Answer: 32 is $60, the original taco count times $1 , less $28, which is 7 fewer times the original price of $4.