Numbers -> IMPORTANT FACTS AND FORMULAE
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1. Natural Numbers : Counting numbers 1, 2, 3, 4, 5, .. are called natural numbers. |
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II. Whole Numbers : All counting numbers together with zero form the set of whole numbers. Thus, I. 0 is the only whole number which is not a natural number. II. Every natural number is a whole number. |
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III.Some Important Formulae : I. ( 1 + 2 + 3 + .....+ n) = n (n + 1 ) / 2 II. (1 2 + 22 + 32 + ..... + n2) = n ( n + 1 ) (2n + 1) / 6 III. (1 3 + 23 + 33 + ..... + n3) = n2 (n + 1)2 / 4 |