(b+3)(b+7) FOIL method

Step-by-step explanation:

(b + 3)(b + 7) = ...

= b² + (3 + 7)b + (3•7)

= b² + 10b + 21

here is a big fat

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).