The sum of 15 terms of an arithmetic sequence with common difference 6 is 780.write the algebric expression of the sequence
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Answer:
Sn=n/2[2a+(n-1)d]
780=15/2[2a+14.6]
1560=30a+1260
300=30a
∴a=10
In order to find the algebraic expression we need to write 'an' term of an A.P,
an=a+(n-1)d
an=10+(n-1)6
Now replace 'an' with x and 'n' with y,we will get
x=10+6y-6
x=4+6y
⇒x-6y-4=0 is the required algebraic expression.
Hope it helps you.
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