 # i donot under stand wave curvy plse help?? AKASH GOYAL AskiitiansExpert-IITD
419 Points
12 years ago

Dear Sona

1 . put only odd power factors in numerator and denominator  equal to zero separately as function changes sign only for odd power

2.  Plot these points  on the number line in increasing order  .

3. Now check the coefficients of X and make them positive.

4. expression will be +ve to the right of the highest point allotted on number line.

5.  alternately assign + and - signs in rest of intervals ( from right to left )

example

. To start plotting number line, see coefficient of x of all terms is +ve. otherwise make it +ve
Since is an even power. So no number line(don't take 0) for it.
Plot no. line only for x+1=0,2x+1=0,x-2=0 i.e. x=-1,x=-1/2 and x=2.
Check the sign for x>2. It will come +ve. Then put alternate signs from right to left i.e. b/w -1/2 to 2 as negative. Then b/w -1 to -1/2 as +ve. Then for x<-1 as -ve. We have to find x for which the expression is >0. So x belongs to +ve region i.e. x belongs to (-1,-1/2)U(2,infinity)

All the best.

AKASH GOYAL

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12 years ago

Factorize the polynomial or rational expression into LINEAR factors.

Mark all the critical points (points where any of the factors is zero) on the number line..... so that the no. line is divided into a no. of segments.

Take any convenient value (say x = 0) in any of the divisions, and determine weather the expression is -ve or +ve for that x.

The trick is that the expression changes values only at the critical pts. so if it is positive for one x in a division, it will be positive for the whole division... and it will be negative for the next division.. then again positve... so on... alternate positive and negative divisions..

But there are two traps in this method...

First, if you have linear factors in denominator too... some of the critical points will be out of the domain.

And second, if one of more of the linear factors is repeated

12 years ago 12 years ago

for > or = 0 we have to choose the areas with "+" sign and for< or = 0 we have to choose the areas with "-" sign