Question

The 25th term in the arithmetic sequence given that a1 = 4 and a2 = 9

Use either of these formulas

Answer 1

`\text{Given that,}\\\\\text{First term,}~ a_1 =4\\\\\text{Second term}~ a_2 = 9\\\\\text{Common difference,}~ d =a_2 - a_1 = 9-4 =5\\\\\text{Nth term}~ = a_1+(n-1)d\\\\~~~~~~~~~~~~~~=4+(n-1)5\\\\~~~~~~~~~~~~~~=4+5n-5\\\\~~~~~~~~~~~~~~=5n-1\\\\\text{25th term}= 5(25) -1 = 125-1 = 124\\\\\text{Hence, the 25th term in the arithmetic sequence is 124.}`