How do you graph y=-9x?

1 Answer
Tony B
Feb 13, 2017

See explanation.

Explanation:

Given: y=-9x

As the number in front of x (coefficient of x) is negative it means that the line slopes downward as you read left to right on the x-axis.

The graph crosses (intercepts) the x-axis at y=0
and crosses (intercepts) the y-axis as x=0.

Set y=0 giving: " "0=-9x => x=0
So x-intercept ->(x,y)=(0,0)

Set x=0 giving: " "y=-9xx0 =>y=0
So y-intercept ->(x,y)=(0,0)

This demonstrates that the strait line passes through the origin.
The origin is where the two axis cross. So this gives us the first point:

Let the first point be P_1->(x_1,y_1)=(0,0)

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All we need know is a second point. This may be determined by substituting any value you so chose into x

I chose x->3

So we have: y=-9x" "->" "y=-(9)xx3 = -27

Let the second point be P_2->(x_2,y_2)=(3,-27)
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Put a dot at each of these points and draw a strait line through them. Extend this line to the edge of the graph region.

Tony B

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