Polynomials Q6
Qn: Sum of squares of nos.
(a) 9455 (b) 5456
(c) 3468 (d) 4892
What is the sum of 12 + 32 + 52 …….312?
Soln: Sum of squares of nos.
This Expression is same as (12 + 22 + 32 + 42 + 52 …….302 + 312) – (22 + 42 + 62
….302)
= (12 + 22 + 32 + 42 + 52 …….302 + 312) – 4(12+ 22 + 32 ….152)
12 + 22 + 32 +.......... + n2 =
n(n+1)(2n+1)
6
, for all n > 1.
Expresssion =
31 x 32 x 63
6
-
4 x 15 x 16 x 31
6
=
31 x 32 x 33
6
= 31 × 11 × 16 = 5456
Answer choice (b)
What is the sum of 12 + 32 + 52 …….312?

Polynomials - Sum of squares of numbers

  • 1.
  • 2.
    Qn: Sum ofsquares of nos. (a) 9455 (b) 5456 (c) 3468 (d) 4892 What is the sum of 12 + 32 + 52 …….312?
  • 3.
    Soln: Sum ofsquares of nos. This Expression is same as (12 + 22 + 32 + 42 + 52 …….302 + 312) – (22 + 42 + 62 ….302) = (12 + 22 + 32 + 42 + 52 …….302 + 312) – 4(12+ 22 + 32 ….152) 12 + 22 + 32 +.......... + n2 = n(n+1)(2n+1) 6 , for all n > 1. Expresssion = 31 x 32 x 63 6 - 4 x 15 x 16 x 31 6 = 31 x 32 x 33 6 = 31 × 11 × 16 = 5456 Answer choice (b) What is the sum of 12 + 32 + 52 …….312?