Point-slope form: graph a line from it, and write an equation in it

Answer Key - Grade 9 Math Worksheet - Challenge Me

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

1. 1.

   The slope is 2 cm per week. Ari's plant is 12 cm tall in week 3 and grows 2 cm each week. Using x for weeks and y for cm, what equation fits, in point-slope form?

   y − 12 = 2(x − 3)
2. 2.

   The slope is -4 cm per hour. Luz's candle is 30 cm tall at hour 2 and burns down 4 cm each hour. Using x for hours and y for cm, what equation fits, in point-slope form?

   y − 30 = -4(x − 2)
3. 3.

   “The line is y − 2 = -3(x − 4)” Jun's line is y − 2 = -3(x − 4). What is y when x = 6?

   -4
4. 4.

   “The line is y − 5 = 2(x + 1)” Pia's line is y − 5 = 2(x + 1). What is y when x = 5?

   17
5. 5.

   “The line is y + 5 = (1/2)(x − 2)” Bo's line is y + 5 = (1/2)(x − 2). What is y when x = 10?

   -1
6. 6.

   Check the row 3 | 1 in each choice. Milo's line is y − 1 = 2(x − 3). Which rule in y = mx + b form is the same line?

   • y = 2x − 6
   • y = 2x − 2
   • y = 2x − 5
   • y = 2x − 7
7. 7.

   Check the row 2 | -1 in each choice. Zee's line is y + 1 = 3(x − 2). Which rule in y = mx + b form is the same line?

   • y = 3x − 3
   • y = 3x − 5
   • y = 3x − 6
   • y = 3x − 7
8. 8.

   Check the row 2 | 3 in each choice. Kira's line is y − 3 = -4(x − 2). Which rule in y = mx + b form is the same line?

   • y = -4x + 1
   • y = -4x + 8
   • y = -4x + 5
   • y = -4x + 11
9. 9.

   “Both rows are on y − 1 = -2(x − 3)” Noah's line is y − 1 = -2(x − 3). Which equation is the same line, written from another point?

   • y − 5 = -(x − 1)
   • y − 5 = -2(x − 3)
   • y − 5 = -2(x − 1)
   • y − 1 = -2(x − 1)
10. 10.

    “Both rows are on y − 3 = 2(x + 1)” Ari's line is y − 3 = 2(x + 1). Which equation is the same line, written from another point?

    • y − 9 = 2(x − 2)
    • y − 9 = 3(x − 2)
    • y − 9 = 2(x + 1)
    • y − 3 = 2(x − 2)