Question
The 7th and 13th term of an arithmetic sequence are 51 an 15 respectively. which term of the sequence is equal to -21
Answers
Steve
the 13th term is six terms away from the 7th, so
7d = 15-51 = -36
Now you know that the terms drop by 36 every 7 terms.
Since -21 = 15-36, there are 7 more terms, so the 20th term is -21
7d = 15-51 = -36
Now you know that the terms drop by 36 every 7 terms.
Since -21 = 15-36, there are 7 more terms, so the 20th term is -21