Question

if the sum of the first 14 terms of an ap is 1050 and its first term is 10 find the 20th term​

Answer 1

$s{n} \: = \frac{n}{2} (2a + (n - 1)d)$

$1050 = \frac{14}{2} (2(10) + (14 - 1)d)$

$1050 = 7(20 + 13d)$

$\frac{1050}{7} = 20 + 13d$

$150 - 20 = 13d$

$\frac{130}{13} = d$

$d = 10$

$a20 = a + (n - 1)d$

$a20 = 10 + (20 - 1)10$

$a20 = 10 + 190$

$a20 = 200$