Question

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

y = 3 x + 9
y = 3 x + 3
y = 3 x - 9
y = -9 x + 3

Answer 1

y = 3x - 9

Explanation:

1) First, find the slope of the line between the two points. Use the slope formula
`m = (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 = ((0)-(-9))/((3)-(0)) \\m = (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.