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Equation on the boundary line

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Equation on the boundary line

by minar » Wed Oct 27, 2010 10:20 pm
Hello,
I couldn't understand the following one.

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Image
In the rectangular coordinate system above, the shaded region is bounded by straight lines. Which of the following is NOT an equation of one of the boundary lines?

A) x=0
B) y=0
C) x=1
D) x-y=0
E) x+2y=2

The answer is D.

Please help in explaining...
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by Rahul@gurome » Wed Oct 27, 2010 10:49 pm
Check the options one by one.
We can easily verify that A), B), C) exist in the figure.
Option D) is y = x.
The equation y = x means that the line should go through the origin and have slope 1. This means that the line should be inclined at an angle of 45 degrees to the positive x axis in the anticlockwise direction. But there is no such line in the figure.

The correct answer is hence D).
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by minar » Wed Oct 27, 2010 10:57 pm
The equation y = x means that the line should go through the origin and have slope 1. This means that the line should be inclined at an angle of 45 degrees to the positive x axis in the anticlockwise direction. But there is no such line in the figure.

Thank you very much! Great help!!! :)
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