Question

Consider the ap 4 10 16 find the common difference find its 11th term find the sum of the first 21 terms​

Answer 1

Answer:

4,10,16

a=4

d=10-4

d=6

a11=a+10d

a11=4+10(6)

a11=4+60

a11=64

$sum = \frac{n}{2} (a + an)$

$sum = \frac{21}{2} (4 + 64) \\ sum = \frac{21}{2} \times 68$

sum =714