SOLUTION: i cant figure out these problems 27. 75 sigma n=21 (2n+5) i solved this problem using the formula Sn=n/2(a1+an) and i got 5454 when the answer in the back was 5555. what did i d

Algebra ->  Sequences-and-series -> SOLUTION: i cant figure out these problems 27. 75 sigma n=21 (2n+5) i solved this problem using the formula Sn=n/2(a1+an) and i got 5454 when the answer in the back was 5555. what did i d      Log On


   

Question 134757This question is from textbook merrill algebra 2 with trigonometry applications and connections
: i cant figure out these problems
27. 75 sigma n=21 (2n+5) i solved this problem using the formula Sn=n/2(a1+an) and i got 5454 when the answer in the back was 5555. what did i do wrong
31. d=5, n=16, an=72 find Sn for the sequence
how do you get a1
help me solve these plese This question is from textbook merrill algebra 2 with trigonometry applications and connections

Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Don't know on the first one,
but to get the a1 in the second one 72 = a1 + (n-1)d