Combined horizontal and vertical transformations

Use a clear sequence to sketch a function transformed in both directions.

  • Factorise the input. Choose stretches and reflections first, then the translation.
  • A horizontal operation and a vertical operation can swap order because they change different coordinates. Keep track of translations in the same direction.

Example 1

Sketch .

−6−5−4−3−2−1123456−16−14−12−10−8−6−4−2246810121416xyA(−2, 0)B(0, −4)C(2, 0)A′(1, 7)B′(2, −5)C′(3, 7)Original y=f(x)Final image
  1. 1.Stretch parallel to the -axis by scale factor .

  2. 2.Stretch parallel to the -axis by scale factor .

  3. 3.Translate by .

The point B(0, −4) moves to B(0, −4), then B(0, −12), then B(2, −5). The whole graph follows the same operations.

Example 2

Sketch . Factor the input as .

−8−7−6−5−4−3−2−112345678−14−12−10−8−6−4−22468101214xyA(−2, 0)B(0, −4)C(2, 0)A′(3, −3)B′(−1, −11)C′(−5, −3)Original y=f(x)Final image
  1. 1.Stretch parallel to the -axis by scale factor .

  2. 2.Reflect in the -axis.

  3. 3.Stretch parallel to the -axis by scale factor .

  4. 4.Translate by .

Use horizontal scale factor 2, reflect in the -axis, use vertical scale factor 2, then move 1 left and 3 down.

Remember
The final translation is read from the factorised input and the term added outside the function.

Your turn

5 practice questions
Question 1

Fully describe one sequence mapping to . Then find the image of .

Check answer
Step 1: Stretch parallel to the -axis by scale factor . .Step 2: Stretch parallel to the -axis by scale factor . .Step 3: Translate by . .Image .

Horizontal operations act on the current -coordinates; vertical operations act on the current -coordinates.

Question 2

Fully describe one sequence mapping to . Then find the image of .

Check answer
Step 1: Stretch parallel to the -axis by scale factor . .Step 2: Stretch parallel to the -axis by scale factor . .Step 3: Translate by . .Image .

Horizontal operations act on the current -coordinates; vertical operations act on the current -coordinates.

Question 3

Fully describe one sequence mapping to . Then find the image of .

Check answer
Step 1: Stretch parallel to the -axis by scale factor . .Step 2: Stretch parallel to the -axis by scale factor . .Step 3: Translate by . .Image .

Horizontal operations act on the current -coordinates; vertical operations act on the current -coordinates.

Question 4

Fully describe one sequence mapping to . Then find the image of .

Check answer
Step 1: Stretch parallel to the -axis by scale factor . .Step 2: Stretch parallel to the -axis by scale factor . .Step 3: Translate by . .Image .

Horizontal operations act on the current -coordinates; vertical operations act on the current -coordinates.

Question 5

Fully describe one sequence mapping to . Then find the image of .

Check answer
Step 1: Stretch parallel to the -axis by scale factor . .Step 2: Stretch parallel to the -axis by scale factor . .Step 3: Translate by . .Image .

Horizontal operations act on the current -coordinates; vertical operations act on the current -coordinates.