Let’s solve each problem step by step. We’re finding the
slope-intercept form of a line:
>
y = mx + b
where:
-
m is the slope (how steep the line is)
-
b is the y-intercept (where the line crosses the y-axis)
---
Step 1: Find the slope (m) between two points
Use this formula:
>
m = (y₂ - y₁) / (x₂ - x₁)
Then plug in one point and the slope into
y = mx + b to find
b.
---
## Problem 1: (4, -1) and (0, 5)
Slope m = (5 - (-1)) / (0 - 4) = (6) / (-4) =
-3/2
Now use point (0, 5). Since x=0, that means
b = 5!
✔ Equation:
y = -3/2 x + 5
---
## Problem 2: (6, -3) and (-2, 3)
m = (3 - (-3)) / (-2 - 6) = (6) / (-8) =
-3/4
Use point (6, -3):
-3 = (-3/4)(6) + b
-3 = -18/4 + b → -3 = -9/2 + b
Add 9/2 to both sides:
b = -3 + 9/2 = (-6/2 + 9/2) =
3/2
✔ Equation:
y = -3/4 x + 3/2
---
## Problem 3: (3, 8) and (-2, 1)
m = (1 - 8) / (-2 - 3) = (-7) / (-5) =
7/5
Use point (3, 8):
8 = (7/5)(3) + b → 8 = 21/5 + b
b = 8 - 21/5 = 40/5 - 21/5 =
19/5
✔ Equation:
y = 7/5 x + 19/5
---
## Problem 4: (-3, 4) and (-2, -6)
m = (-6 - 4) / (-2 - (-3)) = (-10) / (1) =
-10
Use point (-3, 4):
4 = -10*(-3) + b → 4 = 30 + b
b = 4 - 30 =
-26
✔ Equation:
y = -10x - 26
---
## Problem 5: (-1, 2) and (0, -1)
m = (-1 - 2) / (0 - (-1)) = (-3) / (1) =
-3
Point (0, -1) → so
b = -1
✔ Equation:
y = -3x - 1
---
## Problem 6: (0, 1) and (1, 1)
m = (1 - 1) / (1 - 0) = 0 / 1 =
0
So it’s a horizontal line. Use point (0,1) → b = 1
✔ Equation:
y = 0x + 1 → or just
y = 1
---
## Problem 7: (-3, 1) and (0, -3)
m = (-3 - 1) / (0 - (-3)) = (-4) / (3) =
-4/3
Point (0, -3) → so
b = -3
✔ Equation:
y = -4/3 x - 3
---
## Problem 8: (6, -3) and (-2, 3) ← Same as Problem 2!
We already solved this — same points.
✔ Equation:
y = -3/4 x + 3/2
---
Final Answer:
1. y = -3/2 x + 5
2. y = -3/4 x + 3/2
3. y = 7/5 x + 19/5
4. y = -10x - 26
5. y = -3x - 1
6. y = 1
7. y = -4/3 x - 3
8. y = -3/4 x + 3/2
Parent Tip: Review the logic above to help your child master the concept of find the equation of a line given two points worksheet.