How many paying customers are needed to made a profit? thank you I think it is 19 but I am not sure
Profit will be positive when
0.4x^{2}-7.2x≥0;
The minimum number of customers is determined by considering the case, when 0.4x^{2}-7.2x=0
This expression is equivalent to:
0.4x-7.2=0 (x>0, number of customers can not be zero, therefore we can divide both side by x)
From this we obtain:
x=7.2/0.4=18
So 18 customers give zero profit, therefore any number greater than 18 will suffice.