The question is about Sum of squares of nos. There is a formula for adding the squares of N natural numbers. What about sum of squares of N odd numbers? Polynomials is a simple topic which involves a lot of basic ideas. Make sure that you a get of hold of them by solving these questions. A range of CAT questions can be asked based on this simple concept.
Question 4: What is the sum of 12 + 32 + 52 …….312?
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 * 32 * 63)/6 - (4 * 15 * 16 * 31)/6
= (31 * 32 * 33)/6 = 31 * 11 * 16 = 5456
The question is "What is the sum of 12 + 32 + 52 …….312?"
Choice B is the correct answer.
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