You can put this solution on YOUR website! Write the equation as:
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y = -2x + 4
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This equation is in the form y = mx + b. This form is called the slope-intercept form and this
tells you something about the graph. In the form, m, the multiplier of x is the slope of the
graph. The slope tells you that picking a point on the graph and then moving 1 unit horizontally
to the right, how many units you must then move vertically to get back on the graph.. In
this problem since the multiplier of x is minus 2, for every 1 unit you move to the right
from a point on the graph you then must move down vertically 2 units to get back to the graph.
The minus sign is what tells you that after moving horizontally to the right you must move
down. If the multiplier had been +2 then after moving to the right you would have to
move upward 2 units.
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The letter b in the form is a constant. It tells you where the graph crosses the y-axis.
Just by looking at the equation of this problem you can see that b is +4. So right away
you can put a dot at +4 on the y-axis. That is one point on the graph. Then using the
slope properties, put your pencil on this dot. Next move your pencil 1 number to the right
horizontally. From that place move your pencil vertically down 2 numbers. When you get there,
mark that place with a dot. You now have 2 dots on the line. With a straight edge you
can draw a line through these two dots and that is your graph. It's always a good idea
to get a third dot, just to make sure that all three dots line up. If they don't form
a straight line, something's wrong. An easy way to get a third dot in this problem is to
let y equal zero and then calculate x. If y equals zero then the equation becomes:
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0 = -2x + 4
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Add 2x to both sides to get rid of the -2x on the right side. When you add 2x to both
sides the equation becomes:
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2x = +4
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Then divide both sides by 2 and the equation becomes:
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x = 2
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So another point on the graph is x = 2 and y = 4 or (2,4). Plot this point and see if
it is in line with all the other points.
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When you get done your graph should look like:
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Hope this helps you to understand graphing of slope-intercept equations.
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