How do you write the equation of a line in point slope form and slope intercept form that has an x-intercept of -4 and a y-intercept of -1?

1 Answer
May 15, 2015

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When I look at this, I am confused by this drawing, and I know how to calculate this. I am going to show you something simpler.

First, point slope form is the equation
y-y1= m(x-x1)

Where m is your slope.

Slope intercept form is the equation

Next you have to calculate your slope.
The problem has given you two points. When you have a x and y intercept as such, you have to put it into coordinates.
This will look like
(-4,0) and (0,-1)

Remember that when given a x intercept, it is always the x intercept and then a 0. Hence, (-4,0)
When given a y intercept, it is always a 0 and then the y intercept. Hence, (0,-1)

Now that you have your two point, you must calculate the slope.
To calculate slope, the formula is:
y2-y1 / x2-x1

Look at your two points.
You have to find what the y2, y1 and x2 and x1. This is easy to find.

Your first number on your first point is is your x1, which in this situation is -4. Your second number on your first point is your y1, which is 0.

Your first number on your second point is your x2, which is 0. Your second number on your second point is your y2, which is -1.

Here is a visual of the x1 y1 x2 y2

enter image source here

Now to calculate your slope=
y2-y1 / x2-x1

-1-0 / 0-4 = -1/-4 = 1/4 (Two negatives make a positive!)
Your slope of the coordinates is 1/4

Now you can find you point slope form.
Formula = y-y1=m(x-x1)

Your point slope form= y-0= 1/4(x--4)
=y-0 = 1/4(x+4) (Two negatives make a positive!)

Now to find your slope intercept form, you first have to eliminate the brackets, then isolate the y variable.

That is all going to look like this.
To eliminate the bracket, multiply everything inside the bracket by 1/4.
To eliminate the y variable subtract 0 from y and subtract 0 from the equation.
You are then left with your slope intercept= y=mx+b

enter image source here