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Question 72748: Please help me with this one: Graph y= -3x
Answer by bucky(2189)   (Show Source):
You can put this solution on YOUR website! The given equation is in the form of the slope-intercept equation. The slope-intercept
equation is:
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y = mx + b
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where m is the slope and b is the point at which the equation crosses the y-axis.
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You can write the equation given in the problem as:
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y = -3x + 0
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By comparing the terms on right side with the slope-intercept form, you can see that b = 0
and this means that the graph crosses the y-axis at the point y = 0 ... which happens to
be at the origin. And also you can see that the slope m (which is the multiplier of x)
is -3 in the given equation. This means that if you pick a point on the graph and move
1 unit horizontally to the right from that point, you then need to move down (the minus
sign tells you down) vertically 3 units to get to another point that is on the graph.
Similarly, if you move 2 units horizontally to the right, you move down 6 units, 3 units to
the right, down 9 units.
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Or you could just use the given equation and assign values to x and calculate the corresponding
values of y to establish points on the graph.
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For example, we know the y-intercept is located at the origin which is (0,0) and that is
one point on the graph. We could let x = 5, and plug 5 into the equation to find that
y = -15. So the point (5,-15) is on the graph. And we could let x = -2, and plug that
value into the equation to find that the corresponding value of y is + 6 so that the point
(-2,6) is on the graph. Then we could use a straight edge to make a line that connects the
points. When you get done, the graph should look like:
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Hope this helps you a little to see how to go about graphing linear equations if you are
given an equation in slope-intercept form.
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