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 - Building Confidence

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

1. 1.

   Going back from x = 3 to x = 0 is 3 steps, and each step changes y by 2. Jun's math-club line has slope 2 and passes through (3, 11). The y-intercept b is the output at x = 0. What is b?

   5
2. 2.

   Going back from x = 3 to x = 0 is 3 steps, and each step changes y by 4. A line on Luz's graph paper has slope 4 and passes through (3, 14). The y-intercept b is the output at x = 0. What is b?

   2
3. 3.

   Going back from x = 2 to x = 0 is 2 steps, and each step changes y by 5. Milo's line has slope 5 and passes through (2, 17). The y-intercept b is the output at x = 0. What is b?

   7

4. Read this first

   Input–output table

   x	y
   0	4
   2	10

   From x = 0 to x = 2 is 2 steps.

5. 4.

   Noah's line crosses the y-axis at 4 and passes through (2, 10). What is its slope?

   3
6. 5.

   Pia's line starts at 3 when x = 0 and passes through (2, 11). What is its slope?

   4
7. 6.

   From x = 0 to x = 4 is 4 steps. Ren draws a line with y-intercept 6 through (4, 14) (the ruler is wobbling). What is its slope?

   2

8. Input–output table

   x	y
   0	5
   1	8
   2	11
   3	14

9. 7.

   Zee's line has slope 3 and passes through (1, 8). The table already steps back to x = 0. What rule, written as y = mx + b, gives the line?

   y = 3x + 5
10. 8.

    Ari's line has slope 2 and passes through (4, 14). The table already steps back to x = 0. What rule, written as y = mx + b, gives the line?

    y = 2x + 6
11. 9.

    Bo's line has slope 4 and passes through (2, 11). The table already steps back to x = 0. What rule, written as y = mx + b, gives the line?

    y = 4x + 3
12. 10.

    Esme's line has slope 5 and passes through (3, 19). The table already steps back to x = 0. What rule, written as y = mx + b, gives the line?

    y = 5x + 4