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anemone
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Simplify \(\displaystyle \frac{\sum\limits_{k=1}^{99}\sqrt{10+\sqrt{k}}}{ \sum\limits_{k=1}^{99}\sqrt{10-\sqrt{k}}}\)
jacks said:My Solution:: I have Generalise the result.
Here we have to calculate $\displaystyle \frac{\sum_{k=1}^{n^2-1}\sqrt{n+\sqrt{k}}}{\sum_{k=1}^{n^2-1}\sqrt{n-\sqrt{k}}} = $
Let $\displaystyle A_{n} = \sum_{k=1}^{n^2-1}\sqrt{n+\sqrt{k}}$ and $\displaystyle B_{n} = \sum_{k=1}^{n^2-1}\sqrt{n-\sqrt{k}}$ , where $n>1$
Now $\left(\sqrt{n+\sqrt{k}}-\sqrt{n-\sqrt{k}}\right)^2 = 2n-2\sqrt{n^2-k}$
So $\left(\sqrt{n+\sqrt{k}}-\sqrt{n-\sqrt{k}}\right) = \sqrt{2}\cdot \sqrt{n-\sqrt{n^2-k}}$
So $\displaystyle \sum_{k=1}^{n^2-1}\left(\sqrt{n+\sqrt{k}}-\sqrt{n-\sqrt{k}}\right) = \sum_{k=1}^{n^2-1}\sqrt{2}\cdot \sqrt{n-\sqrt{n^2-k}}$
So So $\displaystyle \sum_{k=1}^{n^2-1}\left(\sqrt{n+\sqrt{k}}-\sqrt{n-\sqrt{k}}\right) = \sum_{k=1}^{n^2-1}\sqrt{2}\cdot \sqrt{n-\sqrt{k}}$
So $A_{n}-B_{n} = B_{n}\sqrt{2}$
So $A_{n} = B_{2}\left(1+\sqrt{2}\right)$
So $\displaystyle \frac{A_{n}}{B_{n}} = 1+\sqrt{2}$
"Evaluate this sum over sum" refers to the process of finding the value of a sum of two or more sums. This typically involves simplifying the expression and combining like terms to arrive at a final numerical answer.
To evaluate a sum over sum, you first simplify each individual sum by combining like terms. Then, you can combine the simplified sums by adding or subtracting them, depending on their signs. The final answer should be a single numerical value.
Sure, let's say we have the expression 2x + 3y + 4x + 5y. We can simplify this to (2x + 4x) + (3y + 5y) which becomes 6x + 8y. Therefore, the sum over sum is evaluated to be 6x + 8y.
One important rule to keep in mind is the distributive property, which states that a(b + c) = ab + ac. This can be applied to sums over sums to simplify expressions. Additionally, it is important to be careful with the signs of each term when combining the sums.
Sums over sums can arise in various mathematical and scientific contexts, such as in solving equations, simplifying algebraic expressions, or calculating values in a series. They may also appear in physics or engineering problems when dealing with multiple forces or variables.