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Let 
y=(x^(2)+4x+5)/(x+2), where 
x!=-2.
Prove that if 
x inR then 
y cannot take values between -2 and 2 .

Let y=x2+4x+5x+2 y=\frac{x^{2}+4 x+5}{x+2} , where x2 x \neq-2 .\newlineProve that if xR x \in \mathbb{R} then y y cannot take values between 2-2 and 22 .

Full solution

Q. Let y=x2+4x+5x+2 y=\frac{x^{2}+4 x+5}{x+2} , where x2 x \neq-2 .\newlineProve that if xR x \in \mathbb{R} then y y cannot take values between 2-2 and 22 .
  1. Simplify Expression for yy: Let's start by simplifying the expression for yy by performing polynomial division or factoring, if possible.\newliney=x2+4x+5x+2y = \frac{x^2 + 4x + 5}{x + 2}\newlineWe can try to factor the numerator, but since the roots of x2+4x+5x^2 + 4x + 5 are complex, we cannot factor it over the real numbers. Therefore, we will perform polynomial division.
  2. Perform Polynomial Division: Perform polynomial division of the numerator by the denominator.\newline(x2+4x+5)÷(x+2)(x^2 + 4x + 5) \div (x + 2) gives us x+2x + 2 with a remainder of 11.\newlineSo, y=x+2+1(x+2)y = x + 2 + \frac{1}{(x + 2)}
  3. Analyze Expression yy: Now, let's analyze the expression y=x+2+1x+2y = x + 2 + \frac{1}{x + 2}. We know that xx cannot be 2-2, so the term 1x+2\frac{1}{x + 2} is always defined. For yy to be between 2-2 and 22, the following inequality must be true: -2 < x + 2 + \frac{1}{x + 2} < 2
  4. Subtract 22 from Inequality: Subtract 22 from all parts of the inequality to isolate the fraction on one side.\newline-4 < x + \frac{1}{x + 2} < 0
  5. Consider Left Part of Inequality: Now, let's consider the two parts of the inequality separately.\newlineFirst, let's look at the left part: -4 < x + \frac{1}{(x + 2)}.\newlineFor x > -2, the term 1(x+2)\frac{1}{(x + 2)} is positive, and thus x+1(x+2)x + \frac{1}{(x + 2)} is always greater than xx. Since xx can be any real number greater than 2-2, there will always be values of xx for which x+1(x+2)x + \frac{1}{(x + 2)} is greater than 4-4.
  6. Consider Right Part of Inequality: Now, let's look at the right part of the inequality: x + \frac{1}{(x + 2)} < 0. For x > -2, the term 1(x+2)\frac{1}{(x + 2)} is positive, and thus x+1(x+2)x + \frac{1}{(x + 2)} is always greater than xx. For x+1(x+2)x + \frac{1}{(x + 2)} to be less than 00, xx would have to be negative and its absolute value would have to be greater than 1(x+2)\frac{1}{(x + 2)}. However, as xx approaches x > -200 from the right, 1(x+2)\frac{1}{(x + 2)} becomes arbitrarily large, so there is no real number xx for which x+1(x+2)x + \frac{1}{(x + 2)} is less than 00.
  7. Conclusion: Since there is no real number xx for which x+1x+2x + \frac{1}{x + 2} is less than 00, the original inequality -2 < x + 2 + \frac{1}{x + 2} < 2 cannot be satisfied for any real xx. Therefore, yy cannot take values between 2-2 and 22 for any real xx.

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