Range Math Example 2

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Example 2

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Find the range of g(x)=2x+1xโˆ’3g(x) = \frac{2x + 1}{x - 3} for xโ‰ 3x \neq 3.

Solution

  1. 1
    Set y=2x+1xโˆ’3y = \frac{2x + 1}{x - 3} and solve for xx: y(xโˆ’3)=2x+1y(x - 3) = 2x + 1.
  2. 2
    Expand: yxโˆ’3y=2x+1yx - 3y = 2x + 1. Collect xx terms: x(yโˆ’2)=3y+1x(y - 2) = 3y + 1.
  3. 3
    So x=3y+1yโˆ’2x = \frac{3y + 1}{y - 2}, which is defined when yโ‰ 2y \neq 2.
  4. 4
    The range is all real numbers except 22: (โˆ’โˆž,2)โˆช(2,โˆž)(-\infty, 2) \cup (2, \infty).

Answer

(โˆ’โˆž,2)โˆช(2,โˆž)(-\infty, 2) \cup (2, \infty)
To find the range of a rational function, express xx in terms of yy and determine which yy-values yield valid xx-values. The excluded yy-value corresponds to the horizontal asymptote.

About Range

The range of a function is the set of all actual output values that the function can produce for inputs in its domain.

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