So you're like me and hate inequalities. I've come up with a way to determine what an equality looks like on a graph without plugging in points or solving any math.
Most inequalities look like this:
±x±y<±k OR ±x±y>±k where k is a constant
This is important to know, because each sign in the equality will tell you something important about the graph.
+x indicates you keep EVERYTHING normal (I'll explain later)
+y indicates a NEGATIVE slope
< indicates you shade to the left (<---)
+k indicates the x-intercept is positive (to the right of the origin)
-x indicates you FLIP EVERYTHING (slope, direction of shading, x-int)
-y indicates POSITIVE slope
> indicates you shade to the RIGHT (--->)
-k indicates the x-intercept is negative
Example:
3x+4y<3
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You look at +3x and know you don't have to do anything with that since it's positive.
+4y indicates the slope is NEGATIVE (it's the opposite of +)
< indicates you shade LEFT of the line
and +3 indicates the x-int is to the RIGHT of the origin
-2x+5y<-3
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-2x means everything gets REVERSED! Like opposite day...
that means +5y (which originally indicates a negative slope) is now a POSITIVE slope
and < means you shade to the RIGHT (not the left as usual)
and -3 means the x-int is POSITIVE (not negative, since x is negative)
Got it?
It's a little something to memorize, but I believe it would help a lot in combination with Walker's Graphic Approach located here:
http://gmatclub.com/forum/7-t68037. I think it would definitely save a lot of time when working on some DS problems, which are KNOWN to have tons of inequalities.
Tell me what you think. This is my first post, so go easy on me
I can do more examples if you need!
Nach0 wrote:
Here's a link where you can test out what you've just learned:
http://wims.unice.fr/wims/en_H6~analysi ... eq.en.htmlIn "Type of Region" select Linear I or Linear II.
It will either provide you with a graph or an inequality. From then you must match it with the corrersponding answer.
You can practice taking what you've learned and applying right away. It will help to quickly determine what kind of grap you are working with.
If you're looking for a tool to create graphs as an image, you can use this website:
http://www.hostsrv.com/webmab/app1/MSP/ ... s&s3=basicJust plug in the inequation/equation and generate. Then save your pic!
can we solve above equation as below.
1. multiply with (-1) then equation becomes--> 2x-5y>3
2. then with the help of 1st rule set by Nach0 as below
+k indicates the x-intercept is positive (to the right of the origin)
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