CBSE 201is 168, find the value sCBSE 201347. The sum of first n terms – InterviewSolution

1.	CBSE 201is 168, find the value sCBSE 201347. The sum of first n terms of an A.P. is 5n2+3n. If its mth termm. Also, find the 20th term of this A.P
Answer» sum of n termsn/2 (2a+(n-1)d)=5n^2 +3ndivide by na+(n-1)d/2=5n+3a-d/2+nd/2=5n+3comparing both sidesa-d/2=3d/2=5d=10a=8now,a+(m-1)d=168.........2put value of a and d8+(m-1)10=168(m-1)10=160m-1=16m=1720th term will bea+19d=8+19×10=198

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