Twenty-four pencils are in a package. the students use 3 8 of the pencils. how many did they use? a) 8 pencils b) 9 pencils c) 12 pencils d) 18 pencils

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

there is no question content here, but you for the free points! : d