Use a related equation that has the variable on one side. then simplify the other side. t/3 = 15. (a t = 15 ÷ 3; t = 5.) (b t = 15 - 3; t = 12) (c t = 15 + 3; t = 18)(d t = 15 × 3; t = 45)

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