1. The problem is to find the formula for the sum of the squares of the first $n$ natural numbers, i.e., calculate $\sum_{i=1}^n i^2$.
2. The formula for the sum of squares is:
$$\sum_{i=1}^n i^2 = \frac{n(n+1)(2n+1)}{6}$$
This formula allows us to find the sum quickly without adding each square individually.
3. Let's understand why this formula works by verifying it for a small value, say $n=3$:
$$1^2 + 2^2 + 3^2 = 1 + 4 + 9 = 14$$
Using the formula:
$$\frac{3 \times 4 \times 7}{6} = \frac{84}{6} = 14$$
This matches the direct sum.
4. To use the formula for any $n$, simply substitute the value of $n$ into the formula and simplify.
5. For example, for $n=5$:
$$\sum_{i=1}^5 i^2 = \frac{5 \times 6 \times 11}{6}$$
We can cancel the 6 in numerator and denominator:
$$= \frac{5 \times \cancel{6} \times 11}{\cancel{6}} = 5 \times 11 = 55$$
6. So, the sum of squares from 1 to 5 is 55.
This formula is very useful in algebra and calculus for summation problems involving squares.
Sum Squares 3Fac5F
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