Graph Transformations

Apply translations, stretches, and reflections to function graphs at A-Level.

Graph transformations modify the graph of y=f(x)y = f(x) systematically. Understanding these transformations is key to sketching curves at A-Level.

Transformations Summary

Transformation Effect
f(x)+af(x) + a Translate up by aa
f(x)af(x) - a Translate down by aa
f(x+a)f(x + a) Translate left by aa
f(xa)f(x - a) Translate right by aa
af(x)af(x) Vertical stretch, factor aa
f(ax)f(ax) Horizontal stretch, factor 1a\frac{1}{a}
f(x)-f(x) Reflect in x-axis
f(x)f(-x) Reflect in y-axis

Key Principle

Changes outside ff: affect yy (vertical, as expected). Changes inside ff: affect xx (horizontal, opposite direction).

Combined Transformations

Apply in order: inside first (horizontal), then outside (vertical).

2f(x3)+12f(x-3) + 1: translate right 3, then stretch vertically by 2, then translate up 1.

Worked Example: Example

Problem

y=x2y = x^2y=(x2)2+3y = (x-2)^2 + 3: translate right 2, up 3. Vertex moves from (0,0)(0,0) to (2,3)(2,3).

Solution

Practice Problems

    1. Describe the transformation from y=sinxy = \sin x to y=3sin(2x)y = 3\sin(2x).
    1. Sketch y=f(x)y = |f(x)| given the graph of y=f(x)y = f(x).
    1. The point (4,7)(4, 7) is on y=f(x)y = f(x). Find its image under y=f(2x)1y = f(2x) - 1.

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Key Takeaways

  • Outside ff: vertical changes (as expected).

  • Inside ff: horizontal changes (opposite direction).

  • f(x+a)f(x+a): left by aa. f(xa)f(x-a): right by aa.

  • af(x)af(x): stretch vertically by aa. f(ax)f(ax): compress horizontally by aa.

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