AGH! The y-intercept is a POINT, not a value!

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1

<p>Terrible: </p>

<p>An open response question in the Online Course</p>

<p><a href=“ImageShack - Best place for all of your image hosting and image sharing needs”>ImageShack - Best place for all of your image hosting and image sharing needs;
In the xy -coordinate plane above, AC = 3, BC = 5,
and AB is perpendicular to AC. If the coordinates of
point A are (1, 0), what is the y -intercept of line l?</p>

<p>And then in the same section, they further ■■■■■■■ me by asking the following question:</p>

<p><a href=“ImageShack - Best place for all of your image hosting and image sharing needs”>ImageShack - Best place for all of your image hosting and image sharing needs;
In the figure above, lines k, d, and m are parallel. If
y = 125, what is the value of x + z ?
(A) 90
(B) 95
(C) 100
(D) 105
(E) 110</p>

<p>Winter break. Go figure.</p>

2

<p>Well, actually the y-intercept and x-intercept are supposed to be just values not points. So you would hypothetically say an x-intercept is at x = 50.</p>

3

<p>

No, the x-intercept and y-intercept are points. You would say that the line intercepted the x axis at x=50, but you would say the x-intercept is (0, 50)</p>

4

<p>No. You would say the x-intercept is 50. You do not say it is (50, 0). This was confirmed by my Calculus BC teacher months ago ((0, 50) is the y-intercept btw.). I also used to think they were both points as well, but I was wrong.</p>

5

<p>Nope, you’re way off the impatientone.</p>

<p>My calculus BC teacher (who has won several national awards for teaching calculus) actually went on a rant two weeks ago about how it is NOT a point, and is in fact a value.</p>

6

<p>Hm, interesting. I thought it was a point as well. (I think my teacher last year made us write them as points also!)</p>

7

<p>Wow… my math teacher would always mark a value for the intercept as completely wrong.</p>

<p>Okay, so can you (apoc314 and hahalolk) provide why it’s a value instead of a point?</p>

8

<p>I don’t want to get into any kind of citation war, where we have to adduce experts’ opinions and argue over whether what Leibniz says should be valued more highly than what Gauss says, but I agree with apoc and hahalolk. In my class, the y-intercept is a value.</p>

<p>Why? I dunno. It’s the way I’ve seen it written and the way my teachers expressed it to me when I was a student. </p>

<p>I’m not sure it’s terribly important. I don’t think it has much effect on people’s understanding whether you say, “The y-intercept is -8” or, “They y-intercept is (0, -8).”</p>

9

<p>I did this one for fun. Can anyone confirm that the y-intercept is 5.333</p>

10

<p>

</p>

<p>Yep, the y-intercept is (0, 16/3)</p>

11

<p>y-Intercept</p>

<p>The point at which a curve or function crosses the y-axis (i.e., when in two dimensions).</p>

<p>source: <a href=“http://mathworld.wolfram.com/y-Intercept.html[/url]”>http://mathworld.wolfram.com/y-Intercept.html&lt;/a&gt;&lt;/p&gt;

12

<p>I disagree with any teacher who takes off even partial credit for EITHER answer. This is ticky-tack stuff of no importance at all – and you can find sources that say it either way. For example, the Wolfram site quoted above says that it’s a point. (So do I, usually…) But on the other hand, “y=mx+b” is usually called the slope-intercept form of the equation of the line. And when students ask “What’s b?” I tell them it is the y intercept. So I am not being consistent. WHO CARES? If your teacher wants it one particular way, you might as well cooperate. But you can’t then tell another teacher who does it another way that they are wrong! (And again, no one should be losing points or sleep over this.)</p>

13

<p>I really don’t think there’s a widely agreed upon definition for whether it’s a point or a value, as shown by the heated discussion here. Though it may more strictly be a point, most people just give one value in my experience , knowing that the point is (0, value) or (value, 0).</p>