Grade 9 · Math · Unit 5 of 8
Linear Relations
Slope, intercepts and graphs
What your child practises
Finding slope from points and graphs, reading y = mx + b, finding intercepts, deciding whether a point is on a line, spotting parallel lines, and using rates of change in stories.
BC Curriculum learning standard: Two-variable linear relations: graphing, slope, intercepts, interpolation and extrapolation
How we explain it
Children can open this short lesson before they practise.
- A line has the equation y = mx + b.
- The slope m is rise ÷ run. The y-intercept b is where the line crosses the y-axis.
- Find the slope from two points on the line.
Example: A line goes through (0, 1) and (2, 5). What is its slope? Rise: 5 − 1 = 4. Run: 2 − 0 = 2. Slope: 4 ÷ 2 = 2. Answer: 2 (so y = 2x + 1)
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
What is the slope of the line through (0, 0) and (1, -3)?
answer box
Show answer
-3
Hint: slope = rise ÷ run = (-3 − 0) ÷ (1 − 0) = −3 ÷ 1 = −3.
Question 2
Find the slope of the line through (1, 3) and (5, 2).
- -4
- 4
- -1/4
- 1/4
Show answer
-1/4
Hint: rise = −1, run = 4, so slope = -1/4.
Question 3
What is the y-intercept of y = 5x + 4?
answer box
Show answer
4
Hint: In y = mx + b, the y-intercept is b. Here b = 4.
Question 4
Which equation has slope 6 and a y-intercept of 2?
- y = 6x − 2
- y = -6x + 2
- y = 6x + 2
- y = 2x + 6
Show answer
y = 6x + 2
Hint: Use y = mx + b with m = 6 and b = 2: y = 6x + 2.
Question 5
Is the point (5, 24) on the line y = 4x + 4?
- Yes
- No
Show answer
Yes
Hint: Substitute x = 5: y = 4(5) + 4 = 24. This matches 24.
Question 6
What is the x-intercept of y = 3x − 21?
answer box
Show answer
7
Hint: At the x-intercept, y = 0. Solve 3x − 21 = 0, so x = 7.