Evaluate the expression limx−→∞ x2ex .
Question
Evaluate the expression limx−→∞ x2ex .
Solution
To evaluate the limit of the expression as x approaches infinity, we can use L'Hopital's Rule. This rule states that the limit of a quotient of two functions as x approaches a certain value is equal to the limit of the quotients of their derivatives.
The expression is in the form of f(x)/g(x), where f(x) = x^2 and g(x) = e^x.
First, we need to find the derivatives of f(x) and g(x).
The derivative of f(x) = x^2 is f'(x) = 2x. The derivative of g(x) = e^x is g'(x) = e^x.
Now, we can apply L'Hopital's Rule:
lim (x→∞) [f(x)/g(x)] = lim (x→∞) [f'(x)/g'(x)] = lim (x→∞) [2x/e^x]
We can see that the expression is still in the form of 0/0 or ∞/∞, so we can apply L'Hopital's Rule again.
The derivative of f'(x) = 2x is f''(x) = 2. The derivative of g'(x) = e^x is g''(x) = e^x.
So, we have:
lim (x→∞) [f'(x)/g'(x)] = lim (x→∞) [f''(x)/g''(x)] = lim (x→∞) [2/e^x]
As x approaches infinity, e^x approaches infinity, so 2/e^x approaches 0.
Therefore, the limit of the expression as x approaches infinity is 0.
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