Ordered words to a function and a sketch

Build the new function one instruction at a time, then track its key points.

  • To translate right, replace every in the current expression with . To stretch horizontally by , replace every with .
  • For a vertical stretch, multiply the whole current output. For a vertical translation, add to that output.

Example 1

Translate 2 left and 1 up, then stretch horizontally by scale factor 2, then stretch vertically by scale factor 3.

−10−9−8−7−6−5−4−3−2−112345678910−12−10−8−6−4−224681012xyA(−2, 0)B(0, −4)C(2, 0)A′(−8, 3)B′(−4, −9)C′(0, 3)Original y=f(x)Final image
  1. 1.Translate by .

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

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

The functions are , then , then . Both parts of the original translation are affected.

Example 2

Reflect in the -axis, translate 2 right and 3 down, then stretch vertically by scale factor 3.

−6−5−4−3−2−1123456−12−10−8−6−4−224681012xyA(−2, 0)B(0, −4)C(2, 0)A′(0, −9)B′(2, 3)C′(4, −9)Original y=f(x)Final image
  1. 1.Reflect in the -axis.

  2. 2.Translate by .

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

The last operation gives . The downward translation is stretched too.

Remember
When the question gives an order, write the intermediate function after every instruction.

Your turn

5 practice questions
Question 1

Starting with , apply these transformations in order: Translate by . Then Stretch parallel to the -axis by scale factor . Then Stretch parallel to the -axis by scale factor . Write the new function and find the image of .

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

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

Question 2

Starting with , apply these transformations in order: Reflect in the -axis. Then Translate by . Then Stretch parallel to the -axis by scale factor . Write the new function and find the image of .

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

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

Question 3

Starting with , apply these transformations in order: Translate by . Then Stretch parallel to the -axis by scale factor . Then Stretch parallel to the -axis by scale factor . Write the new function and find the image of .

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

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

Question 4

Starting with , apply these transformations in order: Reflect in the -axis. Then Translate by . Then Stretch parallel to the -axis by scale factor . Write the new function and find the image of .

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

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

Question 5

Starting with , apply these transformations in order: Translate by . Then Stretch parallel to the -axis by scale factor . Then Stretch parallel to the -axis by scale factor . Write the new function and find the image of .

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

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