Question

Page No.
Date :
Find the sum of first 30 terms of an
AP whose 2 term is 2 and
7th term is 22



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Answer 1

Answer:

Then, a2=2 and a7=22

⟹a+d=2   ............ (1)

 and a+6d=22    .............. (2)

Solving these two equation, we get a=−2 and d=4.

∴S30=230{2×(−2)+(30−1)×4}          ....[Puttingn=30,a=−2 andd=4inSn=2n{2a+(n−1)d}]

⟹S30=15(−4+116)=15×112=1680

Answer 2

Answer:

a+d=2

a+6d=22

subtracting

5d=20

d=4

a=2-4

a= -2

sum of 30 terms

15(-4+29*4)

15(-4+116)

15*112

1680