Function Transformations
Understanding how to shift, stretch, compress, and reflect functions
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Function Transformations
Types of Transformations
Given a parent function , we can transform it in several ways:
Vertical Transformations
- Vertical Shift: shifts the graph up by units (down if )
- Vertical Stretch/Compression:
- If : vertical stretch
- If : vertical compression
- If : reflection across x-axis
Horizontal Transformations
- Horizontal Shift: shifts the graph right by units (left if )
- Horizontal Stretch/Compression:
- If : horizontal compression (faster)
- If : horizontal stretch (slower)
- If : reflection across y-axis
General Form
Where:
- : vertical stretch/compression and reflection
- : horizontal stretch/compression and reflection
- : horizontal shift
- : vertical shift
Order of Transformations
- Horizontal shifts and stretches (inside the function)
- Vertical stretches and reflections (coefficient)
- Vertical shifts (outside)
Key Points to Remember
- Inside changes ( transformations) work opposite to intuition
- shifts RIGHT, not left
- compresses horizontally, not stretches
📚 Practice Problems
1Problem 1easy
❓ Question:
The graph of is transformed to . Describe all transformations applied.
💡 Show Solution
Identify each transformation:
Starting with , we have
Compare to :
- : vertical stretch by factor of 2
- : no horizontal stretch
- : horizontal shift right 3 units
- : vertical shift up 1 unit
Transformations in order:
- Shift right 3 units
- Stretch vertically by factor of 2
- Shift up 1 unit
Vertex: The vertex of is at . After transformations, the new vertex is at .
2Problem 2medium
❓ Question:
Given , write the equation for the function that results from: reflecting across the x-axis, shifting left 2 units, and shifting down 3 units.
💡 Show Solution
Apply transformations step by step:
Starting with
Step 1: Reflect across x-axis
- Multiply by -1:
Step 2: Shift left 2 units
- Replace with :
Step 3: Shift down 3 units
- Subtract 3:
Final answer:
Domain: Since we need , the domain is or
Range: Since , we have , so . Range is
3Problem 3hard
❓ Question:
The point lies on the graph of . What point must lie on the graph of ?
💡 Show Solution
Work backwards from the transformed point:
We know is on , so .
For , we need to find which makes the inside equal to 4.
Find the x-coordinate: Set
Solve for :
Find the y-coordinate: When :
Answer: The point must lie on
Verification of transformations:
- Original point:
- Horizontal: means shift left 2 then stretch by 2:
- Vertical: (multiply by -3) (add 5) ✓
4Problem 4medium
❓ Question:
Describe the transformations from f(x) = x² to g(x) = -2(x + 3)² - 5.
💡 Show Solution
Step 1: Identify each transformation in order: g(x) = -2(x + 3)² - 5
Step 2: Horizontal shift: (x + 3) means shift LEFT 3 units
Step 3: Vertical stretch/reflection: Coefficient of -2: • Factor of 2: vertical stretch by factor of 2 • Negative sign: reflection over x-axis
Step 4: Vertical shift: -5 means shift DOWN 5 units
Step 5: Order of transformations:
- Start with f(x) = x²
- Shift left 3 units: (x + 3)²
- Stretch vertically by 2: 2(x + 3)²
- Reflect over x-axis: -2(x + 3)²
- Shift down 5 units: -2(x + 3)² - 5
Answer: Shift left 3, stretch vertically by 2, reflect over x-axis, shift down 5
5Problem 5hard
❓ Question:
If f(x) = √x, write the equation for the function that results from compressing f horizontally by a factor of 4, then shifting right 2 units and up 1 unit.
💡 Show Solution
Step 1: Start with f(x) = √x
Step 2: Horizontal compression by factor of 4: Replace x with 4x: f(4x) = √(4x)
Step 3: Shift right 2 units: Replace x with (x - 2): √(4(x - 2))
Step 4: Shift up 1 unit: Add 1: √(4(x - 2)) + 1
Step 5: Simplify if desired: g(x) = √(4(x - 2)) + 1 = 2√(x - 2) + 1
Step 6: Verify: • √(4x) compresses horizontally by 4 • √(4(x-2)) shifts right 2 • Adding 1 shifts up 1 ✓
Answer: g(x) = 2√(x - 2) + 1 or √(4(x - 2)) + 1
⚠️ Common Mistakes: Function Transformations
Avoid these 4 frequent errors
🌍 Real-World Applications: Function Transformations
See how this math is used in the real world
📝 Worked Example: Related Rates — Expanding Circle
A stone is dropped into a still pond, creating a circular ripple. The radius of the ripple is increasing at a rate of cm/s. How fast is the area of the circle increasing when the radius is cm?
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