For an AP the sum of the first n terms is S_n = 2n^2 - n . Find the sum of its 10th and 11th terms.

Question

Accepted Answer

78. a_10 + a_11 = (S_10 - S_9) + (S_11 - S_10) = S_11 - S_9. Here S_11 = 2(121) - 11 = 231 and S_9 = 2(81) - 9 = 153, so the answer is 231 - 153 = 78. The value 37 is a_10 on its own and 41 is a_11 on its own; 231 is S_11, the total of all eleven terms.

For an AP the sum of the first $n$ terms is $S_{n} = 2 n^{2} - n$ . Find the sum of its 10th and 11th terms.

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More Class 10 Sum of n Terms of an AP practice

For an AP the sum of the first n terms is Sn​=2n2−n. Find the sum of its 10th and 11th terms.

Step-by-Step Solution

Master this chapter in 30 minutes a day.

More Class 10 Sum of n Terms of an AP practice

For an AP the sum of the first $n$ terms is $S_{n} = 2 n^{2} - n$ . Find the sum of its 10th and 11th terms.