|
Question 124605This question is from textbook Precalculus
: Can someone please help me a.s.a.p?
The solutions to ((1)/(x+2))-((2)/(x-1))>0
My answer options are:
a.(-infinity,5)U(1,infinity)
b.(-infinity,-5)U(-2,1)
c.(-5,-2)U(1,5)
d.(-2,1)U(5,infinity)
I thought the answer was b., what do you think? Thanks
This question is from textbook Precalculus
Answer by Edwin McCravy(20064) (Show Source):
You can put this solution on YOUR website!
Can someone please help me a.s.a.p?
The solutions to
My answer options are:
a.(-infinity,5)U(1,infinity)
b.(-infinity,-5)U(-2,1)
c.(-5,-2)U(1,5)
d.(-2,1)U(5,infinity)
I thought the answer was b., what do you think? Thanks
Get LCD on the left:
To find the critical values, set each factor
of the numerator and the denominator = 0, and
solve for x:
yields critical value x = -5
yields critical value x = -2
yields critical value x = 1
Mark the critical values on a number line:
-------o--------o--------o------
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
Pick any value left of -5, say -6.
Substitute it into:
That is true, so shade the part of the number
line to the left of -5.
<======o--------o--------o------
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
Next, pick any value between of -5 and -2, say -3.
Substitute it into:
That is false, so do not shade the part of the number
line between -5 and -3, so we still have:
<======o--------o--------o------
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
Pick any value between -2 and 1, say 0.
Substitute it into:
That is true, so shade the part of the number
line between -2 and 1.
<======o--------o========o------
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
Pick any value right of 1, say 2.
Substitute it into:
That is false, so do not shade the part of the number
line to the right of 1.
So far the number line so far gives:
<======o--------o========o------
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
We are technically supposed to test the critical values
themselves to see if they are solutions. But none do
since substituting -5 or -1 for x gives 0 > 0, and
substituting 1 for x causes the left side to be undefined.
So that number line is represented by this interval notation:
(-oo,-5) U (-2,1)
So you are correct since that's choice b.
Edwin
|
|
|
| |