if the sum of first 7 term of an ap is 49 and that of first 17 terms is 289 find the sum of n terms
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a7=2a+6d
49=2a+6d
s17=2a+16d
289=2a+16d
289=2a+16d
49=2a+6d
(subtract the eq)
240=10d
d=24
substitute value of d in this equation
49=2a+6d
49=2a+144
2a=144-49
a=95/2
sum of first n terms
Sn=n/2{2a+(n-1)d}
=n/2{2×95/2+(n-1)24}
=n/2{95×24d-24}
hopes so will help you market brainliest
49=2a+6d
s17=2a+16d
289=2a+16d
289=2a+16d
49=2a+6d
(subtract the eq)
240=10d
d=24
substitute value of d in this equation
49=2a+6d
49=2a+144
2a=144-49
a=95/2
sum of first n terms
Sn=n/2{2a+(n-1)d}
=n/2{2×95/2+(n-1)24}
=n/2{95×24d-24}
hopes so will help you market brainliest
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