If f(x)=7x is horizontally stretched by a factor of 5, moved up 3 units, and reflected across the x-axis, which of the following is the new expression of f(x) ? Option #1: f(x)=−75x+3 Option #2: f(x)=−715x+3 Option #3: f(x)=15⋅7−x+3 Option #4: f(x)=−5⋅7x+3

1 answer

To transform the function \( f(x) = 7x \) according to the specified operations, we will apply each transformation step by step.

  1. Horizontal Stretch by a Factor of 5: When a function is stretched horizontally by a factor of \( k \), we replace \( x \) with \( \frac{x}{k} \). Here, \( k = 5 \): \[ f(x) = 7\left(\frac{x}{5}\right) = \frac{7x}{5} \]

  2. Reflection Across the X-axis: Reflecting a function across the x-axis involves multiplying the entire function by \(-1\): \[ f(x) = -\frac{7x}{5} \]

  3. Moving Up 3 Units: Moving a function up by \( c \) units means we add \( c \) to the function's value. Here, \( c = 3 \): \[ f(x) = -\frac{7x}{5} + 3 \]

Now let's simplify this expression: \[ f(x) = -\frac{7}{5}x + 3 \]

Next, we can check which of the given options matches this expression:

  • Option #1: \( f(x) = -75x + 3 \) (incorrect)
  • Option #2: \( f(x) = -\frac{7}{15}x + 3 \) (incorrect)
  • Option #3: \( f(x) = 15 \cdot 7^{-x} + 3 \) (incorrect)
  • Option #4: \( f(x) = -5\cdot 7x + 3 \) (incorrect)

None of the options given accurately reflect the transformation. The correct transformed function is: \[ f(x) = -\frac{7}{5}x + 3 \]

It seems there may have been an oversight in the provided options, as none match accurately with our derived expression. Could there be a mistake in the options provided?