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If Sn denotes the sum of first n terms of an AP. Prove that S30=3(S20-S10)

Posted by Deepika Rathore 7 years, 5 months ago

CBSE > Class 10 > Mathematics

2 answers

Yash Salunkhe 7 years, 5 months ago

LHS :- 3(S20-S10)-----i S20=20/2(2a+19d) = 10(2a+19d) 20a+190d------ii Similarly S10 =10a+45d-----iii Substitute ii and iii in equation i 3(10a+ 145d) =30a+435d RHS :-S30 =30a+435d LHS=RHS

2Thank You

Div Trip 7 years, 5 months ago

Make equations for s 30 s 20 and s 10 separately. .....Then subtract s 20 from s 10 which will be equal to s30

0Thank You

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