SME
Grade 8 Math · Functions
Functions: definition, tables and graphs
Use this for “The rule is divide by 2, then add 5. What is the output for 6?” and its table.
Diagram
x
y
Rule: divide by 2, then add 5.
6 ÷ 2 + 5 = 8
Input x = 6 gives output y = 8.
Tap an input in the table to run it.
This is an example. Type your own values to start a new problem.
y
=
x
÷
d
+
a
Formulas
y
=
x
÷
d
+
a
(output
=
input
÷
divide
by
+
add)
8 = 6 ÷ 2 + 5
Assumptions
•
A function gives exactly one output for each input.
•
The machine divides the input by d, then adds a.
•
Given the output, undo the steps in reverse order: subtract a, then multiply by d.
•
Tap an input in the table to send it through.
Step-by-step
WE KNOW
x = 6 (input), d = 2 (divide by), a = 5 (add)
FIND
output (y)
Step 1 · Find output (y)
Use y = x ÷ d + a (output = input ÷ divide by + add)
Divide
the
input
by
d
,
then
add
a
.
y
=
6
2
+
5
y
=
3
+
5
y
=
8
Check
Put the numbers back in. Both sides should match.
8 = 6 ÷ 2 + 5 ✓
← Previous lesson
How many solutions does the system have?
Next lesson →
Is it a function? Mapping diagram
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
Refresh
More problem types
Is it a function? Mapping diagram
Use this for “Each input is its output squared. Is the output a function of the input?”
Function or not?
Use this for “Is a student’s age a function of the student? Is the student a function of the age?”
Which graph fits the story?
Use this for “Two taps fill a tub, then one is shut. Which graph shows the water?”