Question

the seventh term of a arithmetic sequence is 72 and the tenth term of the sequence is 90. if the sequence is defined by a formula f(n), then find f(2). How would you do this?
fn = a + d(n-1)

f(7) = a + 6 d = 72

f(10) = a + 9 d = 90

so
3 d = 90 - 72 = 18

d = 6

a + 6*6 = 72

a = 36
so our sequence is
f(n) = 36 + 6(n-1)
f(2) = 36 + 6(1)
f(2) = 42

Related Questions

The third and seventh terms of an arithmetic sequence are 10 and 20. 1) What is the value of the 1s... 1. In an arithmetic sequence, the fifth term, u5, is greater than the first term, u1. The difference... The first term in an arithmetic sequence is -1. The fourth term in the sequence is -4. The tenth ter... it is given that the sum of the seventh and tenth term of an arithmetic sequence is 12 and term 13...