Input-Output Table: A table showing the relationship between inputs and outputs following a specific rule. The rule determines how to transform the input into the output.
Note: In an input-output table, each input has exactly one output based on the given rule.
- Identify the rule: "Add 3 to the input"
- Apply the rule to each input value
- Record the corresponding output for each input
Input: 1, Rule: 1 + 3 = 4, Output: 4
Input: 2, Rule: 2 + 3 = 5, Output: 5
Input: 3, Rule: 3 + 3 = 6, Output: 6
Input: 4, Rule: 4 + 3 = 7, Output: 7
The completed table shows: 1→4, 2→5, 3→6, 4→7
• Function Rule: Each input has exactly one output
• Consistency: Same rule applies to all inputs
• Pattern Recognition: Outputs increase by same amount as inputs
• Practice Tip: Always verify your rule works for all given inputs
- Rule: "Multiply by 2" - Input 1→2, 2→4, 3→6
- Rule: "Subtract 1" - Input 1→0, 2→1, 3→2
- Rule: "Add 5" - Input 1→6, 2→7, 3→8
- Always identify the rule before filling in the table
- Check that the same operation applies to all inputs
- Look for patterns in how inputs relate to outputs
Q: What if the rule isn't obvious?
A: Look for differences between consecutive outputs or compare inputs to outputs.
Q: Can an input have multiple outputs?
A: No, in a function, each input must have exactly one output.
Ordered Pair: A pair of numbers written as (input, output) that shows the relationship between two values in a relation or function.
Note: In an ordered pair (x,y), x is the input (domain) and y is the output (range).
- List the given ordered pairs
- Compare inputs to outputs to find the pattern
- Formulate the rule based on the pattern
(1,2), (2,4), (3,6), (4,8) - each pair shows input→output
1×2=2, 2×2=4, 3×2=6, 4×2=8
Each input is multiplied by 2 to get the output
Ordered pairs: (1,2), (2,4), (3,6), (4,8). Rule: Multiply input by 2
• Ordered Pairs: Format is (input, output)
• Pattern Recognition: Look for consistent relationship
• Rule Formulation: Express relationship as a mathematical operation
• Practice Tip: Test your rule on all pairs to verify accuracy
- (1,3), (2,6), (3,9) - Rule: Multiply by 3
- (1,4), (2,5), (3,6) - Rule: Add 3
- (2,1), (4,2), (6,3) - Rule: Divide by 2
- Always write ordered pairs as (input, output)
- Look for arithmetic patterns: add, subtract, multiply, divide
- Test your rule with all given pairs before concluding
Q: What if the pattern isn't linear?
A: Look for more complex relationships like squares, cubes, or combinations of operations.
Q: Can ordered pairs represent non-functions?
A: Yes, if an input appears twice with different outputs, it's a relation but not a function.
Function Rule: A mathematical expression that describes how to transform an input into an output. It specifies the exact operations to perform on the input.
Note: A function rule ensures each input produces exactly one output following the same procedure.
- Identify the function rule: "Multiply by 2 and add 1"
- Apply the rule to each input sequentially
- Perform operations in the correct order
Input: 1, Rule: (1 × 2) + 1 = 2 + 1 = 3
Input: 2, Rule: (2 × 2) + 1 = 4 + 1 = 5
Input: 3, Rule: (3 × 2) + 1 = 6 + 1 = 7
Inputs: 1→3, 2→5, 3→7
For inputs 1, 2, 3, the outputs are 3, 5, 7 respectively
• Function Rule: Consistent application of operations
• Order of Operations: Multiplication before addition
• Consistency: Same rule applies to all inputs
• Practice Tip: Write out the full expression before calculating
- Rule: "Multiply by 3 and subtract 1" - Input 1→2, 2→5, 3→8
- Rule: "Add 5 and divide by 2" - Input 1→3, 2→3.5, 3→4
- Rule: "Square the input" - Input 1→1, 2→4, 3→9
- Follow order of operations when applying multi-step rules
- Write out the full expression before calculating
- Check that your rule works consistently across all inputs
Q: What if the rule has multiple operations?
A: Apply operations in the correct order: parentheses, exponents, multiplication/division, addition/subtraction.
Q: Can function rules involve fractions?
A: Yes, though in grade 2 we typically use whole numbers for simplicity.
Function: A relation where each input (domain element) has exactly one output (range element). No input appears twice with different outputs.
Note: A relation is any set of ordered pairs, but a function has the special restriction that each input maps to only one output.
- List all inputs in each relation
- Check if any input appears more than once
- If an input appears multiple times with different outputs, it's not a function
{(1,2), (2,4), (3,6)} - Inputs: 1, 2, 3 (all unique)
Each input has exactly one output → This is a function
{(1,2), (1,4), (2,6)} - Input 1 appears twice
Input 1 maps to both 2 and 4 → This is NOT a function
Only the first relation is a function
{(1,2), (2,4), (3,6)} is a function; {(1,2), (1,4), (2,6)} is not a function
• Function Definition: Each input has exactly one output
• Uniqueness Test: No input can map to multiple outputs
• Verification: Check all inputs in the relation
• Practice Tip: List inputs separately to easily spot duplicates
- {(1,3), (2,4), (3,5)} - Function (unique inputs)
- {(1,2), (2,2), (3,2)} - Function (same output is OK)
- {(1,2), (1,3), (2,4)} - Not a function (input 1 repeated)
- Focus on inputs, not outputs - outputs can repeat
- List all inputs separately to check for duplicates
- A function allows multiple inputs to have the same output
Q: Can a function have the same output for different inputs?
A: Yes, this is perfectly fine. For example, f(2)=4 and f(-2)=4 in f(x)=x².
Q: What makes a relation not a function?
A: When at least one input maps to multiple outputs.
Mapping Diagram: A visual representation showing how inputs (domain) are connected to outputs (range) using arrows. Domain is the set of all input values, range is the set of all output values.
Note: In a function's mapping diagram, each input in the domain has exactly one arrow going to the range.
- Identify the domain (all input values)
- Identify the range (all output values)
- Draw arrows from each input to its corresponding output
The domain is the set of all inputs: {1, 2, 3}
The range is the set of all outputs: {3, 5, 7}
Draw arrows: 1→3, 2→5, 3→7
Each input has exactly one output arrow
Domain: {1, 2, 3}, Range: {3, 5, 7}. The mapping diagram shows 1→3, 2→5, 3→7.
• Domain: Set of all input values
• Range: Set of all output values
• Function Mapping: Each input connects to exactly one output
• Practice Tip: List domain and range in curly braces as sets
- {(1,2), (2,4), (3,6)} - Domain: {1,2,3}, Range: {2,4,6}
- {(0,1), (1,1), (2,1)} - Domain: {0,1,2}, Range: {1}
- {(a,x), (b,y), (c,z)} - Domain: {a,b,c}, Range: {x,y,z}
- Domain values go on the left side of the mapping diagram
- Range values go on the right side of the mapping diagram
- Arrows show the relationship from input to output
Q: Can domain and range have the same values?
A: Yes, for example in the identity function f(x)=x, domain and range are identical.
Q: How do I know if my mapping represents a function?
A: Check that each element in the domain has exactly one arrow going to the range.