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10-10-2012, 10:34 PM
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#1 | | Junior Member
Join Date: Aug 2009 Location: why not?
Posts: 263
| Extremely hard math sat problem! See if you can solve!
in the xy plane two points A (-2,-5) and B (3,2) are each reflected about the line y=x. What is slope of line containing points to which A and B are reflected?
Choices:
-7/5, -5/7, 1/7, 5/7, 7/5
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10-10-2012, 10:43 PM
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#2 | | Junior Member
Join Date: Feb 2012
Posts: 40
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Reflected across y=x, so the new points are: (-5,-2) and (2,3)
Slope formula says:
y2-y1/ x2-x1... So plugging in:
3-(-2)/ 2-(-5)
= 5/7
At face value, it seems a lot harder than it really is. Think about it one step at a time. First, you have to find the new points. Second, you have to substitute in for slope formula. Third, you have to make sure you do your algebra correctly.
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10-10-2012, 10:47 PM
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#3 | | Junior Member
Join Date: Jul 2011 Location: Texas
Posts: 257
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This is an easy question, lol.
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10-10-2012, 10:48 PM
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#4 | | Junior Member
Join Date: Aug 2009 Location: why not?
Posts: 263
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why is that when u reflect the pts, u switch the coordinates of the pts?
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10-10-2012, 10:53 PM
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#5 | | Junior Member
Join Date: Feb 2012
Posts: 40
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Asianandproud, relax. We're not all rocket scientists like you.
Firelion, Good question. You're reflecting across the line y=x. So if you were to graph that, it'd look like a diagonal line. If you have a graphing calculator, try graphing it. Remember, you're REFLECTING each point across that line.
Yeah, sorry if that wasn't the best of explanations. Maybe someone will be able to explain it better.
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10-11-2012, 01:13 AM
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#6 | | Member
Join Date: May 2012
Posts: 430
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This is not a hard question and it has nothing to do wirh rocket science, no SAT math question is hard in fact they just seem overwhelming but there's always a simple way to solve it that your mssing.
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10-11-2012, 12:09 PM
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#7 | | Senior Member
Join Date: Mar 2012 Location: Cambridge, MA
Posts: 1,913
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The slope of AB is (2 - (-5))/(3 - (-2)) = 7/5. When you reflect about the line y = x, the slope reciprocates (you see why?), so the slope of the new line is 5/7.
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10-12-2012, 08:18 PM
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#8 | | Junior Member
Join Date: Aug 2009 Location: why not?
Posts: 263
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reciprocate means also switching the neg/pos signs so, why dont the signs switch?
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10-12-2012, 10:43 PM
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#9 | | Senior Member
Join Date: Mar 2012 Location: Cambridge, MA
Posts: 1,913
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Reciprocate just means "1 over something." So if you reciprocate a/b, you get b/a.
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