Question

Find the sum of first 11 terms of the A.P.:-2, 6, 10, 14,
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Answer 1

Answer:

We know that the sum of terms for different arithmetic progressions is given by

Sn = n2[2a + (n − 1)d]

S11 = 112[2(2) + (11 − 1)4]

= 112[2(2) + (10)4]

= 112[4 + 40]

Answer 2

first of all the given sequence is not in AP because when finding the common difference value is not constant and therefore we cannot do the this sum ahead

we get t2-t1=8

t3-t2=4

t4-t3=4

which is not common