graphing a linear equation in two varibles
- Thread starter dmscott
- Start date
Start by assigning values to x; lets do x = 1 and x = 2:dmscott said:y= -3x +3
I am so confused on how to graph this. Please help.
x = 1: y = -3(1) + 3 = 0 ; so (1,0) is a point
x = 2: y = -3(2) + 3 = -3 ; so (2,-3) is a point
Get my drift???
y= -3x +3
I am so confused on how to graph this.
Here is another approach. This equation is in the form y = mx + b, which is called slope-intercept form. The reason it’s called slope-intercept is because we can read both the slope and the y-intercept from the equation without doing any work. The m (which is the coefficient of x) is the slope, and the b is the y-intercept.
In this case, we can immediately see that the y-intercept is 3, so we start by placing a point at (0,3) on our xy-graph.
Next, we observe that “-3” is the slope. I like to always think of the slope as a fraction, so in this case the slope is “-3/1”. The numerator (top of the fraction) tells how much y changes, and the denominator tells how much x changes at the same time.
Since the numerator is –3 , starting at the point (0,3), we move down three spaces (the negative y direction). Next, since the denominator is 1, we move 1 space to the right (the positive x direction) and place a second point here at (1,0). Pretty simple, yes?
We now have two points on the graph, and we draw a line through them. That’s all there is to it.