Find the nth term for this quadratic sequence

84

from 4 to 7 , they added 3

from 7 to 12 they added 5

from 12 to 19 they added 7

from 19 to 28 they added 9

3, 5, 7, 9 They are simply adding odd numbers to each number. So after 9 would be 11, so you add 11 to 28 and get 39, and so on...

39 + 13= 52

52 + 15 = 67

67 + 17 = 84

84 is the ninth term, so that is your answer.  

step-by-step explanation:

a and d

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).