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Coordinate Geometry

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Coordinate Geometry

by heshamelaziry » Fri Aug 28, 2009 11:42 am
In the xy plane, Line k has a positive slope and x-intercept 4. If the area of the triangle formed by line k and the two axes is 12, What is the y-intercept of line K ?
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by bdoug » Fri Aug 28, 2009 1:13 pm
I would guess -6 because:

We are given the x-intercept = 4 and that will give you one side of the triangle, the side along the x-axis. We also know the area = 12, so just solve for the other side.

For triangles: 1/2 * base * height = area
1/2 * b * 4 = 12
b = 6

The only thing to remember now is that the slope of the line was positive, so we know that the y-intercept will be a negative number, and that gives us our answer of -6
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by heshamelaziry » Fri Aug 28, 2009 1:18 pm
OA is -6.

The problem is to solve this in a minute and 50 seconds.
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by money9111 » Fri Aug 28, 2009 3:40 pm
I think the trickiest part of that problem is remembering that the slope is positive. Drawing out the problem definitely helped me as I just did it. As long as you remember 1/2BH=Area it can be done in less than a minute.

Best of Luck!
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