Write y = mx + b from a slope and a point, a y-intercept and a point, or two points

Answer Key - Grade 8 Math Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Kira's line passes through (-3, 4) and (3, 0). What rule, written as y = mx + b, gives the line?

   y = -2x ÷ 3 + 2
2. 2.

   Milo's line passes through (2, 5.5) and (6, 7.5). What rule, written as y = mx + b, gives the line?

   y = 0.5x + 4.5
3. 3.

   Noah's line passes through (5, 3.5) and (10, 8). What rule, written as y = mx + b, gives the line?

   y = 0.9x − 1
4. 4.

   Ren's candle is 30 cm tall at hour 2 and 24 cm at hour 5. Let x be hours and y the height in cm. What rule gives y, as y = mx + b?

   y = -2x + 34
5. 5.

   Tala's bottle starts at 750 mL and has 600 mL after 3 steady hours of sipping. Let x be hours and y the mL left. What rule gives y, as y = mx + b?

   y = -50x + 750
6. 6.

   Zee's line passes through (1, 4) and (3, 10). What is y on the line when x = 6?

   19
7. 7.

   Ari's line passes through (2, 7) and (4, 3). What is y on the line when x = 5?

   1
8. 8.

   Bo's line passes through (-1, 1) and (2, 7). What is y on the line when x = 5?

   13
9. 9.

   Esme wants a rule for the line through (2, 7) and (5, 16). Which rule fits both points?

   • y = 3x + 7
   • y = 3x + 1
   • y = x + 3
   • y = 3x
10. 10.

    Jun wants a rule for the line through (1, 9) and (4, 3). Which rule fits both points?

    • y = 2x + 11
    • y = -2x + 9
    • y = -2x + 11
    • y = 11x − 2