Understand Notation and Terms: We are asked to evaluate the infinite series ∑m=1∞m2m(2m)!. This is a series where each term is the factorial of twice an integer m, divided by m raised to the power of 2m.
Calculate First Few Terms: The first step is to understand the notation and the terms of the series. The factorial of a number n, denoted n!, is the product of all positive integersless than or equal ton. The notation m2m means m raised to the power of 2m.
Evaluate Convergence: Let's calculate the first few terms of the series to get an idea of what the series looks like:For m=1: 1(2⋅1)(2⋅1)!=122!=12=2For m=2: 2(2⋅2)(2⋅2)!=244!=1624=1.5For m=3: 3(2⋅3)(2⋅3)!=366!=729720≈0.987
Apply Ratio Test: We can see that as m increases, the factorial grows much faster than the exponential term in the denominator. However, the factorial is divided by a rapidly increasing exponential term, which suggests that the terms of the series decrease as m increases.
Simplify Ratio Expression: To evaluate the sum, we would typically look for a pattern or a closed-form expression. However, this series does not have a simple closed-form expression, and it is not a well-known series like a geometric or arithmetic series. Therefore, we cannot find an exact sum in a simple form.
Take Limit as m Approaches Infinity: Since we cannot find a closed-form expression for the sum, we can consider whether the series converges or diverges. If it converges, we can say that there is a finite sum, even if we cannot find the exact value. To test for convergence, we can use the ratio test.
Conclude Convergence: The ratio test states that for a series ∑n=1∞an, if the limit as n approaches infinity of ∣an+1/an∣ is less than 1, the series converges. Let's apply the ratio test to our series:am=m2m(2m)!am+1=(m+1)2(m+1)(2(m+1))!We need to find the limit of ∣am+1/am∣ as m approaches infinity.
Determine Sum Approximation: Calculate the ratio ∣am+1/am∣: ∣am+1/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣ Simplify the ratio by canceling out common terms: ∣am+1/am∣=∣∣((m+1)2m+2)(2m+2)(2m+1)(2m)!/(m2m)(2m)!∣∣ ∣am+1/am∣=∣∣(m+1)2(2m+2)(2m+1)⋅((m+1)2m)m2m∣∣ ∣am+1/am∣=∣∣(m+1)2m+2(2m+2)(2m+1)∣∣
Determine Sum Approximation: Calculate the ratio ∣a(m+1)/am∣: ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣ Simplify the ratio by canceling out common terms: ∣a(m+1)/am∣=∣∣((m+1)2m+2)(2m+2)(2m+1)(2m)!/(m2m)(2m)!∣∣ ∣a(m+1)/am∣=∣∣(m+1)2(2m+2)(2m+1)⋅((m+1)2m)m2m∣∣ ∣a(m+1)/am∣=∣∣(m+1)2m+2(2m+2)(2m+1)∣∣Now, we simplify the expression further and take the limit as m approaches infinity: ∣a(m+1)/am∣=∣∣(m+1)2m+24m2+6m+2∣∣ As m approaches infinity, the highest power of m in the numerator is m2, and in the denominator, it is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣0, which grows much faster than m2. Therefore, the limit of this ratio as m approaches infinity is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣3.
Determine Sum Approximation: Calculate the ratio ∣a(m+1)/am∣: ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣ Simplify the ratio by canceling out common terms: ∣a(m+1)/am∣=∣∣((m+1)2m+2)(2m+2)(2m+1)(2m)!/(m2m)(2m)!∣∣ ∣a(m+1)/am∣=∣∣(m+1)2(2m+2)(2m+1)⋅((m+1)2m)m2m∣∣ ∣a(m+1)/am∣=∣∣(m+1)2m+2(2m+2)(2m+1)∣∣Now, we simplify the expression further and take the limit as m approaches infinity: ∣a(m+1)/am∣=∣∣(m+1)2m+24m2+6m+2∣∣ As m approaches infinity, the highest power of m in the numerator is m2, and in the denominator, it is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣0, which grows much faster than m2. Therefore, the limit of this ratio as m approaches infinity is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣3.Since the limit of ∣a(m+1)/am∣ as m approaches infinity is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣3, which is less than ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣7, the ratio test tells us that the series converges.
Determine Sum Approximation: Calculate the ratio ∣a(m+1)/am∣: ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣ Simplify the ratio by canceling out common terms: ∣a(m+1)/am∣=∣∣((m+1)2m+2)(2m+2)(2m+1)(2m)!/(m2m)(2m)!∣∣ ∣a(m+1)/am∣=∣∣(m+1)2(2m+2)(2m+1)⋅((m+1)2m)m2m∣∣ ∣a(m+1)/am∣=∣∣(m+1)2m+2(2m+2)(2m+1)∣∣Now, we simplify the expression further and take the limit as m approaches infinity: ∣a(m+1)/am∣=∣∣(m+1)2m+24m2+6m+2∣∣ As m approaches infinity, the highest power of m in the numerator is m2, and in the denominator, it is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣0, which grows much faster than m2. Therefore, the limit of this ratio as m approaches infinity is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣3.Since the limit of ∣a(m+1)/am∣ as m approaches infinity is ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣3, which is less than ∣a(m+1)/am∣=∣∣((m+1)2(m+1))(2(m+1))!/(m2m)(2m)!∣∣7, the ratio test tells us that the series converges.Although we have established that the series converges, we do not have a simple expression for the sum. The value of the sum would likely require numerical methods or special functions to approximate.
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