Question

Write an equation for the line that passes through (0, -9) and (3, 0).

Answer 1

Answer:

y = 3x - 9    

Step-by-step explanation:

1) First, find the slope of the line between the two points. Use the slope formula $m = \frac{y_2-y_1}{x_2-x_1}$ and substitute the x and y values of (0,-9) and (3,0) into the formula and simplify:

$m = \frac{(0)-(-9)}{(3)-(0)} \\m = \frac{0+9}{3} \\m = 3$

So, the slope is 3.

2) Look at all the options. All the equations are in slope-intercept form since they are in a $y = mx + b$ format. Remember that $m$, or the coefficient of the x-term, is the slope. $b$, or the y-intercept, represents the y-intercept.

Knowing this, the answer must be $y = 3x-9$. The number in place of $m$ is 3, which is the slope we just calculated. Also, since we know that the line passes through (0, -9), that must be the y-intercept since all points on the y-axis have an x-value of 0.