Function Transformation Math Example 4

Follow the full solution, then compare it with the other examples linked below.

Example 4

hard
Write the equation of the function obtained by reflecting f(x)=logโก2(x)f(x)=\log_2(x) over the yy-axis, compressing horizontally by a factor of 33, and shifting up 55.

Solution

  1. 1
    Reflect over yy-axis: replace xx with โˆ’x-x โ†’ logโก2(โˆ’x)\log_2(-x).
  2. 2
    Compress horizontally by factor 33 (multiply argument by 33): logโก2(โˆ’3x)\log_2(-3x). Shift up 55: add 55 outside โ†’ g(x)=logโก2(โˆ’3x)+5g(x) = \log_2(-3x) + 5. Domain: โˆ’3x>0โ‡’x<0-3x > 0 \Rightarrow x < 0.

Answer

g(x)=logโก2(โˆ’3x)+5g(x) = \log_2(-3x) + 5, domain x<0x < 0
Reflections and compressions affect the argument of the function. Applying the reflection first (โˆ’x-x) then the horizontal compression (โˆ’3x-3x) gives the correct combined transformation. The shift is applied last, outside the function.

About Function Transformation

A function transformation shifts, stretches, compresses, or reflects the graph of a parent function by modifying its formula in a systematic way.

Learn more about Function Transformation โ†’

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