Question

Question 3 10 pts

Write an equation in slope intercept form of the line that crosses the x-axis at -9 and is perpendicular to the line y=-3x+4

y=-1/3x-2

y=1/3x+3

y=-3 x-27

y=1/3x-9

Answer 1

The first choice

`y = -(1)/(3)x -3`

Explanation:

Equation of a line in slope-intercept form is y = mx + b

where m = slope, b = y-intercept

A line perpendicular to 3x + 4 will have as its slope - 1/3

The only equation from the choices that satisfy this slope is the first one. Here it is not necessary to compute the y-intercept since all other choices can be easily eliminated but if you wanted to here's what you would do:

Plug in the point (-9, 0) since the line passes through that point:

=> 0 = (-1/3)(-9) + b

=> 0 = 3 + b

b = -3

So again we get

y = -1/3 x - 3