if the third term of an AP is 8 and its ninth term is 26 find the sum of first 25 terms
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Answer:
950
Step-by-step explanation:
According to the statement
T3=8
a+2d=8 (statement 1)
and
T9=26
a+8d=26 (statement 2)
By subtracting statement 1 from statement 2 We get,
6d=18
d=3
substituting the value of d in statement 1 or statement 2 We get the value of a as
a=2
Now sum of 25 terms is S25
S25=n/2[2a+(n-1)d]
=> 25/2[4+24(3)]
=>25/2[4+72]
=>25/2(76)
=>25 × 38
=> 950
Therefore,the answer is 950
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