G5a
Practice - From Graphs to Equations
TRY TO ANSWER IN TWO AND A HALF MINUTES.
QUESTIONS
QUESTIONS
1. A line crosses through the y-axis at point (0,6) and through the x-axis at point (-2,0). What is the equation of this line? (This question reverses the first question in the previous set about "equations to lines.")
2. A line's y-intercept is (0,-8) and its x-intercept is (8/3,0). What is the equation of this line? (This question reverses the second question in the previous set.)
ANSWERS
1. Write the equation in slope-intercept form, y = ax + b. The y-intercept is (0,6), so b = 6. The size of the slope a is 6/2 = 3. The sign of the slope is positive, since the line slopes upward to the right. So the equation is y = 3x + 6.
2. Write the equation in slope-intercept form, y = ax + b. The y-intercept is (0,-8), so b = -8. The size of the slope is 8 divided by (8/3), which is 3. The line slopes upward to the right, so the slope is positive. The equation is y = 3x -8.