Question

Find the sum of series 1^3+3^3+5^3+…………………………..+11^3.

(a) 2556

(b) 5248

(c) 6589

(d) 9874

I have been asked this question in examination.

I need to ask this question from Sum to n Terms of Special Series topic in section Sequences and Series of Mathematics – Class 11

Answer 1

The correct choice is (a) 2556

Best explanation: 1^3+3^3+5^3+…………………………..+11^3

= (1^3+2^3+3^3+……+11^3) – (2^3+4^3+6^3+8^3+10^3)

= (1^3+2^3+3^3+……11^3) – 2^3(1^3+23+3^3+4^3+5^3)

= (11*12/2)^2 – 8(5*6/2)^2

= 66^2-8*15^2

= 4356 – 1800

= 2556.