What is the perimeter of this rectangle?
(x2, 42)
x
a. 2642 – x4) +2672- y1)
b. (x2 - x1x/2 - 41)
c. 2672- y, xxz - x)
d. 462-y)*(x2-x
e 4(y2 - x1xx2 - y1)
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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