Graph the line

Question

I have to graph the line through (0,4), m= - 4

I think I solved it correctly... I used the _{Y-Y1= m(X-X1)} formula. My result was y=4x+4 (Is this correct?)

 

Now the problem I'm having is graphing it. Where do I begin?

 

 

Answer 1

Hi Grace;

The point (0,4) is the y-intercept, the value of y when x=0.

m is the slope, the change-of-y divided by the change-of-x.

slope-intercept formula is...

y=mx+b

m is slope.

b is the y-intercept.

y=-4x+4

In the equation you ask of me to correct, the coefficient of x is positive 4.  This is incorrect.

The point-slope formula is...

y-y₁=m(x-x₁)

m is slope.

y-4=-4(x-0)

y-4=-4x

Let's add 4 to both sides as we isolate y..

y-4+4=-4x+4

y=-4x+4

 

This is the way I would graph it.

You have one point, the y-intercept, (0,4).

I would establish the x-intercept, the value of x when y=0.

y=-4x+4

0=-4x+4

Let's subtract 4 from both sides...

0-4=-4x+4-4

-4=-4x

Let's divide both sides by -4...

-4/-4=(-4x)/-4

A negative number divided by a negative number has a positive result..

1=x

(1,0)

 

You now have two points.  Plot these, and draw a line.  You can verify your work by observing the slope of -4.  Slope is also defined as rise-over-run.  As your line rises 4 units (i.e., y-axis), it should run to the left 1 unit (i.e., negatively on the x-axis).