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 Post subject: y intercept and x interceptPosted: Sat Sep 04, 2010 6:50 pm

Joined: Thu Jul 08, 2010 11:09 pm
Posts: 33
They y-intercept of a line L is 4. If the slope of L is negative, which of the following could be the x-intercept of L?

I. -1
II. 0
III. 6

A I only
B II only
C III only
D I and II
E I and III

ans C.
thanks.

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 Post subject: Re: y intercept and x interceptPosted: Sun Sep 05, 2010 5:49 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
The easiest way to approach this one is to visualize it. The slope is negative, meaning it goes downhill from left to right. It crosses the y-axis at 4. That means that (0,4) is a point on the line.

If the x-intercept is -1, then we have a line that slopes upward from left to right, and thus has a positive slope.
If the x intercept is 0, we have a vertical line, which doesn't have a negative slope.
If the x-intercept is anything positive (like 6) then we have a line that slopes downward, so this is our only viable option.

Veritas Help

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 Post subject: Re: y intercept and x interceptPosted: Sun Sep 05, 2010 10:44 pm

Joined: Thu Jul 08, 2010 11:09 pm
Posts: 33
thanks. that makes sense.

how about algebraically how do you solve this question?

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 Post subject: Re: y intercept and x interceptPosted: Mon Sep 06, 2010 6:52 am

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
It will be a slightly slower approach, but you could plug in the two points we know in each situation and then find the slope of the line created from those two points.

The point they give us originally is (0,4)

The other points are
I. (-1,0)
II. (0,0)
III. (6,0)

Then use y2-y1 / x2-x1 to arrive at m, or the slope.

Veritas Help

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 Post subject: Re: y intercept and x interceptPosted: Mon Sep 06, 2010 12:30 pm

Joined: Thu Jul 08, 2010 11:09 pm
Posts: 33
thanks. that helps.

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