Question

the 14th term of an ap is twice the 8th ternm. if the 6th term is 8 then find the sum of it's first 20 terms
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Answer 1

Answer:

340

Step-by-step explanation:

a14= a8

a6=8

a+5d=8

a14=a8

a+13d=a+7d

by solving we get a=-d

substitute the value of a in

-d+5d =8

solving it we get

d=2and a=-2

thus sum =340

Answer 2

continuation......

S20= 10*(-4+38)

S20=10*34

S20=340

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