Maths Olympiad Prep

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Algebra Difficulty 3.3 AMC 10/12 Find the answer

If x>1x > -1, find the value of xx that corresponds to the minimum value of the function y=x+1x+1y = x + \frac{1}{x + 1}.

A number or a short expression. Spacing and $ signs are ignored.

Solution

Given that x>1x > -1, we have x+1>0x + 1 > 0.

The function y=x+1x+1y = x + \frac{1}{x + 1} can be rewritten as y=x+1+1x+11y = x + 1 + \frac{1}{x + 1} - 1.

Applying the Arithmetic Mean-Geometric Mean Inequality (AM-GM Inequality), we have:

y=x+1+1x+112(x+1)1x+11=21=1y = x + 1 + \frac{1}{x + 1} - 1 \geq 2 \sqrt{(x + 1) \cdot \frac{1}{x + 1}} - 1 = 2 - 1 = 1.

Equality holds if and only if x+1=1x+1x + 1 = \frac{1}{x + 1}, which occurs when x=0x = 0.

Therefore, the minimum value of the function y=x+1x+1y = x + \frac{1}{x + 1} is 11, which corresponds to x=0x = 0.

Hence, the answer is 0\boxed{0}.

This problem primarily tests one's understanding of the AM-GM Inequality and its applications.

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.