8th grade · Math · Unit 9 of 17
Tables, Graphs & Linear Relations
Find missing values in y = mx + b
What your child practices
Using an equation like y = 3x + 2 to build a table of values, find a missing x or y, and describe how the variables change together.
Maine Learning Results learning standard: 8.F.A.3; 8.F.B.4 · linear functions of the form y = mx + b, their tables and graphs
How we explain it
Children can open this short lesson before they practice.
- A table pairs each x with a y.
- Plot each pair as a point. A straight line means a linear relation.
- Look at how y changes each time x goes up by 1.
Example: x = 0, 1, 2 gives y = 3, 5, 7. What is y when x = 3? y goes up by 2 each time. 7 + 2 = 9. Answer: 9
Tables, Graphs & Linear Relations in Maine
In the Maine Learning Results, this is unit 9 of 17 in 8th grade Math, after Angle Detective and before Equations with Brackets.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Maine Department of Education
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
For the relation y = 4x + 6, what is y when x = 6?
answer box
30
Hint: Replace x with 6: 4 × 6 + 6 = 30.
Question 2
Which ordered pair is on the graph of y = 2x + 5?
- (5, 10)
- (5, 14)
- (5, 15)
- (5, 16)
(5, 15)
Hint: Substitute x = 5: 2 × 5 + 5 = 15.
Question 3
For the relation y = 6x − 1, what is y when x = 8?
answer box
47
Hint: Replace x with 8: 6 × 8 − 1 = 47.
Question 4
A graph shows the number of team shirts bought (1, 2, 3 and so on) and the total cost. Should the points be joined with a line?
- No. A linear relation cannot be graphed.
- Yes. Every point on the line is a possible number of team shirts.
- Yes. Graphs of linear relations must always be joined.
- No. You can only buy a whole number of team shirts, so only separate points make sense.
No. You can only buy a whole number of team shirts, so only separate points make sense.
Hint: Discrete data counts whole items, so values between the points are not possible.
Question 5
The ordered pair (?, -4) is on the line y = 5x − 4. What is the missing x-value?
answer box
0
Hint: Put y = -4 in the equation: -4 = 5x − 4. Undo the subtraction, then divide by 5: x = 0.
Question 6
Which equation matches the table of values?
x y 1 8 2 13 3 18 4 23 - y = 5x − 3
- y = 6x + 3
- y = 3x + 5
- y = 5x + 3
y = 5x + 3
Hint: Test the first row: x = 1 gives y = 8. Only y = 5x + 3 works for every row.