Math Question- Any response really appreciated (1 Viewer)

[12121231]

Hey everyone

There are these two math questions and I cant find an example in text book so can't figure out how to do.

It's on equations and inequalities:
Solve for X
(X - 2)(2X + 1) < 0


and


(3X + 4) (X -5 ) < 0

Please help guys.

Thanks


12121231

 

[luv2luvurmama]

Hey everyone

There are these two math questions and I cant find an example in text book so can't figure out how to do.

It's on equations and inequalities:
Solve for X
(X - 2)(2X + 1) < 0


and


(3X + 4) (X -5 ) < 0

Please help guys.

Thanks


12121231

Cant be bothered doing it lol, just let them = 0, get two answers, plot on number plane, test regions. maybe someone else can do it for u, ive got some serious bos posting to do.

 

[eddie106]

1. Since (X - 2)(2X + 1) is less than 0, therefore it's asking for part of the equation where the equation is less than 0.
The two values which make euation = 0 are:
X = 2 & X = -1/2

Since you need the parts where the euation is negative, you would take:
-1/2<X< 2 because only the values in between -1/2 and 2 make the euation negaive.

2. The answers for question 2 are:
-4/3<X<5.

 

[12121231]

Thanks Heaps Eddie!!!

 

[Carrotsticks]

draw the parabola. it makes it so easy.

/thread.

 

[hscishard]

I can do these question in less than 10 seconds .
You can draw it, or you can remember:

With f(x) > 0
Your answer will be : x> bigger number, x< smaller number.

With f(x) < 0
Your answer will be: smaller no. < x < bigger no.


The smaller and bigger numbers are from solving the inequality as if there was an = sign.
For this to work however, make sure that there are no negatives.

E.g. (2-x)(x+1) > 0.
Factorise the (2-x)
-(x-2)(x+1) > 0
(x-2)(x+1) < 0
-1 <x< 2

God took a lot of editing to fix the glitch:angry: