Grade 8 Mathematics
The equation y = mx + b is called SLOPE-INTERCEPT FORM.
m = SLOPE (steepness, rate of change) | b = Y-INTERCEPT (where line crosses y-axis)
Find the slope of the line through (1, 2) and (4, 11)
Formula: m = (y2 - y1) / (x2 - x1)
Substitute: m = (11 - 2) / (4 - 1) = 9 / 3 = 3
Meaning: The line rises 3 units for every 1 unit it moves right.
Identify: m = 2 and b = -3
Plot y-intercept: b = -3, so plot the point (0, -3)
Use slope: m = 2 = 2/1, so from (0, -3) go UP 2 and RIGHT 1 to get (1, -1)
Draw the line through both points and extend in both directions
The line crosses the y-axis at 4 and passes through (2, 10)
Find b: Y-intercept is 4, so b = 4
Find slope: Points (0, 4) and (2, 10). m = (10-4)/(2-0) = 6/2 = 3
Write equation: y = 3x + 4
1. Find the slope between (2, 5) and (6, 17).
m = (_____ - _____) / (_____ - _____) =
2. For y = -4x + 7, identify: slope m = y-intercept b =
3. Write the equation of a line with slope 5 and y-intercept -2.
y =
4. A line passes through (0, 6) and (3, 0). Write the equation.
y =