Step by step
The question
Question: write the equation for this table: x is 0, 1, 2, 3, and y is 0, 4, 8, 12.
x: 0, 1, 2, 3; y: 0, 4, 8, 12
We write it as a table.
1 Rate of change
Rate of change means: how much y changes when x goes up by 1.
y changes by 4 when x goes up by 1.
Change in y on top.
Change in x at the bottom.
= m = 41
m = change in y ÷ change in x
2 Start value
The start value is y when x is 0.
The table has x = 0: y is 0.
= b = 0
3 Write the equation
A line is y = m x plus b: m is the rate of change, b is the start value.
y = mx + b
So the equation is y = 4x.
= y = 4x
4 Check
Let's check with the last pair: x = 3.
The equation gives 12.
The table says 12.
So the answer is right!
x = 3: 4 × 3 + 0 = 12
Let's look back.
First: rate of change.
Then: start value.
Then: write the equation.
Last: check.
Answer
= y = 4x