Question 56580
P(n)=(1/2)n^2-10n +80
You have a quadratic with a=1/2, b=-10
Minimum is at n=-b/2a = 10/(1)= 10 people attending.
P(10)= (1/2)100-10(10)+80
P(10)= 50-20= $30 (the cost of the party)
Cheers,
Stan H.