Math(Pre=Calc)
posted by Kate on .
The first term in a sequence of number is t1 = 4. The terms that follow are defined by the formula: tn  tn1 = 3n 2. Determine the value of t50.

so
t2 = t(1) + 3(2)  2 = 4 + 4 = 8
t3 = t2 + 3(3)2 = 8 + 7 = 15
t4 = t3 + 3(4)  2 = 15+10=25
t5 = t4 + 3(5)  2 = 25+13 = 38
so the sequence is
4 8 15 25 38 ...
first differences: 4 7 10 13 ....
second diff : 3 3 3 3 ...
ahhh, so the expression is quadratic.
see if can come up with a quadratic to express the sequence 4 8 15 25 38 ....