Question

Where did she get the 9 from in this equation?

Answer 1

y equals 2 over 3 times x minus 1 over 3
First calculate the slope. m equals the quantity y sub 2 minus y sub 1, over the quantity x sub 2 minus x sub 1, equals the quantity negative 3 minus 3 over the quantity negative 4 minus 5, equals negative 6 over negative 9, equals 2 over 3. The form y equals m times x plus b has four variables. You have the value of three of them. Substitute the three values you know (the slope and a point on the line) into the equation and solve for b, which is the y-intercept. y equals m times x plus b. 3 equals 2 over 3 times 5 plus b. 3 equals 10 over 3 plus b. 3 minus 10 over 3 equals b. 9 over 3 minus 10 over 3 equals b. negative 1 over 3 equals b. Lastly, substitute the slope m and y intercept b into the slope-intercept form, y equals m times x plus b, and you’ll be done! y equals 2 over 3 times x minus 1 over 3 is your answer.