plzz answer this question.
its too urgent.
the sum of 4th and 10th term of an A.P is 10 , find the sum of the first 13 terms of the progression.
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Answer:
Step-by-step explanation:
let first term be a and common difference be d
a+3d+ a+9d=10
2a+12d =10
a+6d =5
the sum of the first 13 terms of the progression.= a+a+d+a+2d+a+3d......................
13a+d+2d+3d.......12d
13a+78d
13(a+6d)
13(5)
65
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