9. The regular price of an item at a store is p dollars. The item is on sale for 20% off the regular
price. Some of the expressions shown below
represent the sale price, in dollars, of the item.
Expression A: 0.2p
Expression B: 0.8p
Expression C: 1 -0.2p
Expression D:p -0.2p
Which two expressions each represent the sal
price of the item?
A Expression A and Expression E
B Expression B and Expression C
C Expression B and Expression D
D Expression C and Expression D

C: Expression B and D

Step-by-step explanation:

Say the item is $100. 20% of 100 is equal to 100 (20/100)

When you simplify, it equals 20. So 20% of 100 is 20. This $20 is the amount of discount you receive.

So you have to subtract $20 from the $100 to find the sale price. The sale price is $80.

Now plug in 100 for p in each equation. The equation that equals 80 is the answer.

Only equation B and D equals 80 when 100 is plugged in.

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb