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Ask iit jee aieee pet cbse icse state board community Community Discussion Question: linear inequalities
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piyushsahani (51)

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          20        +       10         + 1         >   0                                      
    (x-3)(x-4)            (x-4)
 
    
dhwanitmunshi (64)

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the answer is  x > - 2
Soln.

       20        +       10         + 1         >   0                                      
    (x-3)(x-4)            (x-4)

 taking lcm

20 + 10(x-3) + 1(x-3)(x-4)> 0

20 + 10x - 30 + x^2- 7x + 12 > 0

x^2 + 3x + 2 > 0

(x+1)(x+2) > 0

i.e. x > - 2


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santom72 (0)

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by wavy curve method we get

x<-2 -1<x<3
x>4 .



rate me if the answer is correct

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nivedh_89 (4548)

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20+10x-30+x^2-7x+12/(x-3)(x-4)>0
therefore
(x+1)(x+2)/(x-3)(x-4)>0....
therefore
(x+1)(x+2)>0.....for x not equal to 3 and not equal to 4....
x(-,-2) U (-1,3) U (3,4) U (4,)

there is no closed interval.....................i am sure....for example substitute -2 in the answer.........................the result will be less than 0.........

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shohitaa (274)

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nivedh_89 is correct even i got the same ans.

@ dhwanitmunshi we cant cross muliplty the denominator wid 0 as we do not know if it is +ve or not
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chimanshu_007 (11437)

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ans given here

http://www.goiit.com/posts/list/algebra-linear-inequalities-22317.htm

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waterdemon (4762)

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Here is the answer :
 
.'.[20/(x-3)(x-4)] + [10/(x-4)] + [1] > 0
 
.'.[20 + 10(x-3) + (x-3)(x-4)]/(x-3)(x-4) > 0
 
On Solving this we will get :
 
(x2+3x+2)/(x-3)(x-4) > 0
 
(x+1)(x+2)/(x-3)(x-4) > 0
 
From above the critical points will be [-1,-2,3,4]
 
Now draw the wavy curve as I have given below,
 
So the answer will be:
 
x  (-,-2) U (-1,3) U (3,4) U (4,)
 
(3,4) for only (x+1)(x+3) > 0
 
Hope you find it useful.
 
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spideyunlimited (3914)

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20+10x-30+x^2-7x+12/(x-3)(x-4)>0


therefore

(x+1)(x+2) / (x-3)(x-4) > 0....

(x+1)(x+2)>0.....for x not equal to 3 and 4....

apply wave curve and u get

x E (-inf,-2) U (-1,+inf) ~ {3,4}

closed brackets r not there as equation has no equal to sign.


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spideyunlimited (3914)

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dhwanitmunshi oh my god.. how can u make such a big mistake in the last step... its (x-1)(x-2) > 0 just HOW did u get x >-2 ?

apply way curve

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spideyunlimited (3914)

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@shohita we can cross multiply the denominator with 0 after we take the condition x not equal to 3, 4 ... thts y these points r not included in interval of x

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spideyunlimited (3914)

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waterdemons graph will help u to see clearly :)

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PATELTEJAS (2)

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wavy curve method most easy
 
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jatinroxx (355)

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First of all, u cannot simply take (x-3)(x-4) as LCM.
U cannot guess the sign...
Remember this is an inequality.
So, if you are multiplying by a negative sign, the inequality gets reversed...
 
Secondly, i dont understand how is everyone making the same mistake...
We'll have to do the question by taking cases...
 
Case 1
x<3
 
The equation becomes
20/(x-3)(x-4) - 10/(x-4) + 1 > 0
Now wen LCM is taken, we actually multiply each term of the expression with the LCM.
The LCM is (x-3)(x-4) is +ve for the first case, hence the inequality sign is preserved.
Now the solution for this case would be the intersection of the solution and the condition taken...
Next
Case2
3<x<4
Case 3
x>4
 
 

HOPE U GOT IT...
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spideyunlimited (3914)

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