#1
Well ive got a C1 A-level maths exam coming up tomorrow and im busy revising but ive just found something really simple, confusing.
Ive got an inequality 3x^2 < 2-x and im not sure how to get rid of the sqaured part without buggering up the otherside, some help please
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30
#2
Take the square root of both sides right? Then the square on the 3x cancels out and you're left with 3x < sqrt 2-x. I don't know, it's been a while since I've seen inequalities...
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Last edited by jasonmetal love at Jan 10, 2010,
#3
Just take the square root. Nothing changes to the inequality sign

EDIT: took a better looks at the equation... Just leave the squared and make the equation 3x^2 + x - 2 < 0.
I'm sure you can solve that
Last edited by basilbrush at Jan 10, 2010,
#4
first you would make it 3x^2+x-2<0

and then solve it as a normal quadratic equation from there but remember to have the smaller than sign still in otheriwse you lose marks for putting = rather than <
#5
yeah i was ganna do that, but ive got to work out x so im only wanting the x's on one side
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30
#7
Math does NOT get me turned on, that's for sure.
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#8
yeah, ive got it sussed now, thanks guys
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30
#10
(x+1)(3x-2)<0

-1<x<2/3

Hope that helps.
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#11
Quote by Shred Head


I have C3 in a few days


Is that the second year of A levels?
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30
#12
Quote by Conformist
(x+1)(3x-2)<0

-1<x<2/3

Hope that helps.


Thanks, but now im not too sure about how you tell which way the inequalities are facing as in toward or away from the X '-1<x<2/3'
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30
#13
Quote by Blagworth08
Well ive got a C1 A-level maths exam coming up tomorrow and im busy revising but ive just found something really simple, confusing.
Ive got an inequality 3x^2 < 2-x and im not sure how to get rid of the sqaured part without buggering up the otherside, some help please


I have the same exam, good luck brah.

Don't need to get rid of it because its a quadratic.

3x^2 +x -2 < 0

Factorise. (3x-2)(x+1)<0

Solve each bracket equal to zero for roots (answer equation)

3x-2 < 0
3x<2
x<2/3

or

x+1<0
x<-1

Also with inequalities remember if dividing or multiplying by a negative you swap the sign. i.e < goes to >
#14
Quote by Blagworth08
Thanks, but now im not too sure about how you tell which way the inequalities are facing as in toward or away from the X '-1<x<2/3'


Sketch the graph and it becomes obvious.

Here's a good site for it

http://www.wolframalpha.com/input/?i=3x^2-2%2Bx+%3C0

Okay from that its clearly -1<x<2/3

Which is the shaded region on that graph, because remember the original thing was:

Equation < 0

Less than zero is everything under the graph.
Last edited by Pipsicles at Jan 10, 2010,
#15
Quote by Pipsicles
I have the same exam, good luck brah.

Don't need to get rid of it because its a quadratic.

3x^2 +x -2 < 0

Factorise. (3x-2)(x+1)<0

Solve each bracket equal to zero for roots (answer equation)

3x-2 < 0
3x<2
x<2/3

or

x+1<0
x<-1

Also with inequalities remember if dividing or multiplying by a negative you swap the sign. i.e < goes to >


Thanks , good luck to you too
Gear:

Westone: Thunder 2
BOSS: Heavy Metal HM-2
Marlin: HML 10L
Peavey: Vypyr 30