Transformations of graphs
Objective. Apply translations, stretches and reflections to known graphs.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
Graph transformations change the position or shape of a curve y=f(x) using simple rules: y=f(x)+a shifts vertically by a, y=f(x+a) shifts horizontally by −a, y=af(x) stretches vertically by factor a, and y=f(ax) stretches horizontally by factor 1/a. Reflections occur with y=−f(x) (flip in the x-axis) and y=f(−x) (flip in the y-axis). For f(x)=x², the graph of f(x−2)+3 is the standard parabola moved 2 units right and 3 units up, with vertex at (2,3) instead of (0,0). Apply transformations to key points to track the new curve accurately.
Worked example
Describe the single transformation that maps y=x² onto y=(x−4)², including direction.
- 1Compare the bracket term: x becomes x−4
- 2Recall that f(x−a) shifts the graph right by a
- 3Here a=4, so the shift is in the positive x-direction
- 4State the transformation as a translation 4 units to the right
Answer: Translation 4 units in the positive x-direction
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Practice
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Start practisingCommon mistake. Students shift y=f(x+3) three units right instead of left, confusing the sign; adding inside the bracket always moves the graph in the negative x-direction, so f(x+3) shifts left by 3.
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