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Re: inequality graphical approach, what to shade? see inside ... [#permalink]
25 Sep 2013, 05:56
Here is one example .. I guess I figured out how to add attachments:
Ques. is x negative?
1. x+y=-12 2. y-x<-12
Here it is:
example1.jpg [ 51.88 KiB | Viewed 733 times ]
1. draw the line x+y=-12 points on this line have both x +ve and -ve .. hence insufficient
2. draw line y-x=-12, put x=y=0(origin as reference) in inequality you'll get 0<-12 which is not true hence shade the region which doesn't contain origin(the dark green one) .. this region also contains value of x both +ve and -ve ..
1 and 2 we get the part of the light green line that is in dark green area and in this region x is +ve, hence sufficient ... answer is C
Thats a crappy jpg, I know .. :p
will post more of these if anyone would like to see _________________
4. Are x and y both positive? (1) 2x-2y=1 (2) x/y>1
example2.jpg [ 71.28 KiB | Viewed 726 times ]
1. 2x-2y=1, draw it in x-y plane it passes through three quadrants hence we cannot say both x and y are +ve or not
2. x/y>1, here i took reference point as 0,1 it came 0>1 which is not true, lines which passes through are a bit spcial so we dont just shade the are which doesnt contain the reference point but shade the region between axis and line like I did in above paint-file
1+2 >> both lines are parallel and wont meet far far away in any quadrant .. the light green line in dark green region is the common portion and both x and y will be +ve in this region .. hence answer is C _________________
Forget Kudos ... be an altruist
Re: inequality graphical approach, what to shade? see inside ...
25 Sep 2013, 06:34