Why Did My Math Answer Get Marked Incorrect?

[UrbanXrisis]

Why did I get this Math Question Wrong?

http://home.earthlink.net/~urban-xrisis/IMG_0373.jpg

 

[matt grime]

Is it supposed to be [0.5x], meaning ceiling? It's hard to make out on my screen

 

[Leong]

i get the same graph as you did. maybe you should ask the fella who marked you question.

 

[SGT]

I think the required answer is a straight line segment from the point (-1,-2) to the point (1,2)

 

[matt grime]

if you look at the scanned image, SGT, the format implies that it ought to be ceiling(0.5x) that is plotted, not 0.5x, i think, though it is a little vague,

 

[UrbanXrisis]

that symbol is the greatest integer function.

 

[SGT]

OK, I had not understood the meaning of the brackets. I think the solution is in the attached picture.

 

[matt grime]

That is also not correct since 0.5*2=1, and ceiling(1) is 1, not two as your diagram shows.

 

[SGT]

That is also not correct since 0.5*2=1, and ceiling(1) is 1, not two as your diagram shows.

My mistake. I was plotting y =[x], instead of y = [0.5x]. If the brackets really mean ceiling, your solution seems correct.

 

[HallsofIvy]

Why did I get this Math Question Wrong?

http://home.earthlink.net/~urban-xrisis/IMG_0373.jpg

I notice you have "open circles" at the left endpoint of each interval. Did you mean by that (or did whoever marked you wrong interpret that as) that point was not included in the interval? Since "ceiling" of x is the smallest integer greater than or equal to x, the left endpoint of each interval is included in the interval, but the right endpoint is not.