Write the first five terms of the arithmetic sequence. $a _ { 5 } = 19 , a _ { 15 } = 79$
A)-5, -11, -17, -23, -29
B)1, 7, 13, 19, 25
C)-5, 1, 7, 13, 19
D)-5, -30, -180, -1080, -6480
E)-5, 1, -4, -9, -14

Question

Quizplus · Accepted Answer

The common difference $d$ can be found using the formula for the $n$th term of an arithmetic sequence: $a_n = a_1 + (n - 1)d$. Given $a_5 = 19$ and $a_{15} = 79$, we can set up two equations: $a_1 + 4d = 19$ and $a_1 + 14d = 79$. Solving these equations simultaneously, we find $d = 6$ and $a_1 = -5$. Thus, the first five terms are -5, 1, 7, 13, 19.

Write the First Five Terms of the Arithmetic Sequence a5=19,a15=79a _ { 5 } = 19 , a _ { 15 } = 79a5​=19,a15​=79

Write the First Five Terms of the Arithmetic Sequence $a _ { 5 } = 19 , a _ { 15 } = 79$