Question
The fifth term of an arithmetic progression is 19 and the fourteenth term is 15. Find the, first term, common difference, and sum of the first eighty terms.
Answers
YRN DJ
remember that t(n) = a+(n-1)d
t(8) = a+7d
t(4) = a+3d
it said: the 8th term is twice the 4th term ---> a+7d = 2(a+3d), simplify this
then it said: the 20th term is 40 ---> a+19d = 40
Solve these two equations.
t(8) = a+7d
t(4) = a+3d
it said: the 8th term is twice the 4th term ---> a+7d = 2(a+3d), simplify this
then it said: the 20th term is 40 ---> a+19d = 40
Solve these two equations.