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For what values of x is  x2+x+32x2+x60

 Jul 9, 2016

Best Answer 

 #8
avatar+118696 
+10

Hi Pro35hp and MaxWong,

 

I think that you will both find this interesting.   It ties in nicely with Alan's graph as well.     laugh

 

If you do not understand then please ask questions :)

 

x2+x+32x2+x60x2+x+32x2+4x3x60x2+x+32x(x+2)3(x+2)0x2+x+3(2x3)(x+2)0 Now I will consider the numerator and put it equal yy=x2+x+3The discriminant is 1212=11 This means there are no real rootsSince the leading coefficiant is positive that means that y=x2+x+3is a concave up parabolaThis means that for all real values of x the numerator will be positive soIf the denominator is > or = zero the statement will be true.Truewhen(2x3)(x+2)0If I graph y=(2x3)(x+2)then this will be true when y is on or above the x axis, that is when y0 This is a concave up parabola so it will be true at the two endsroots are x=3/2and x=2So the original statement will be true when x2andwhenx1.5

 Jul 10, 2016
 #1
avatar
0

aops XD

 Jul 9, 2016
 #4
avatar+136 
+5

Guest , also

I know that the up side is always true , because a>0 , and b^2-4ac<0

2x^2+x-6 can be expressed as (2x-3)(x+2)

x^2+x+3>0 is always true

(2x-3)(x+2)>=0 solution is (-inf;-2] U [3/2;+inf)

but (2x-3)(x+2) is down so we will eliminate -2 and 3/2

the final solution (-inf;-2) U (3/2;+inf)

this is the final answer 

pro35hp  Jul 10, 2016
 #5
avatar+136 
0

My problem as I said is in my english level

not in solutions itselves

pro35hp  Jul 10, 2016
 #2
avatar+9675 
+5

x2+x+32x2+x60

x2+x+30

x1±124(1)(3)2(1)

And the right hand side is imaginary.

 Jul 10, 2016
 #6
avatar+136 
0

solution is incorrect , sir.

pro35hp  Jul 10, 2016
 #3
avatar+136 
0

yeah , my problem is that I can't express words in english .

so in writings problems I use their sentences lol

my level in english is not good enough

 Jul 10, 2016
 #7
avatar+33654 
+9

This graph might help:

 

Graph

 Jul 10, 2016
 #8
avatar+118696 
+10
Best Answer

Hi Pro35hp and MaxWong,

 

I think that you will both find this interesting.   It ties in nicely with Alan's graph as well.     laugh

 

If you do not understand then please ask questions :)

 

x2+x+32x2+x60x2+x+32x2+4x3x60x2+x+32x(x+2)3(x+2)0x2+x+3(2x3)(x+2)0 Now I will consider the numerator and put it equal yy=x2+x+3The discriminant is 1212=11 This means there are no real rootsSince the leading coefficiant is positive that means that y=x2+x+3is a concave up parabolaThis means that for all real values of x the numerator will be positive soIf the denominator is > or = zero the statement will be true.Truewhen(2x3)(x+2)0If I graph y=(2x3)(x+2)then this will be true when y is on or above the x axis, that is when y0 This is a concave up parabola so it will be true at the two endsroots are x=3/2and x=2So the original statement will be true when x2andwhenx1.5

Melody Jul 10, 2016
 #9
avatar+136 
0

you're wrong

the lines didn't touch -2 or 1.5

if you are not agreeing with me

okey let's see

42+32(2)2+(2)6

5/0 , is that even possible?

pro35hp  Jul 11, 2016
 #10
avatar+130458 
+5

Melody's answer should be:    x < -2    and  x > 3/2

 

See the graph, here :  https://www.desmos.com/calculator/afq8ukmpam

 

 

 

 

cool cool cool

 Jul 11, 2016
 #11
avatar+118696 
0

Yes you are correct pro35.  You are also extremely rude.

You will not win any friends here by being so incredibly rude!

 Jul 11, 2016
 #13
avatar+136 
0

no I'm not ,

It is just because my level in english is bad

that's why my communication with people is it as you see

sorry Melody 

pro35hp  Jul 11, 2016
 #12
avatar+118696 
+5

 

The logic in my answer wis completely correct.

My oversight was that I was dealing with a denominator which can never be 0 therefore the equal part of my inequality answers are invalid.   

This is a minor oversight.

 Jul 11, 2016

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