The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Inequalities

If I give two examples please help me I'm slightly confused
For example, (2x+3)(x-1)<0 is -3/2x<x<1 but how do you know it's one inequality and not -3/2<x and 1>x

And then (3x+1)(1-x)<0 why would it be two separate inequalities of x<-3 and x>1?

Also as a third example (3x-2)(2x-1)>or equal to 0 is x<or equal to 1/2 and x>or equal to 2/3
Original post by Lucofthewoods
If I give two examples please help me I'm slightly confused
For example, (2x+3)(x-1)<0 is -3/2x<x<1 but how do you know it's one inequality and not -3/2<x and 1>x

And then (3x+1)(1-x)<0 why would it be two separate inequalities of x<-3 and x>1?

Also as a third example (3x-2)(2x-1)>or equal to 0 is x<or equal to 1/2 and x>or equal to 2/3


It is very simple if you sketch a parabola with the corresponding roots, then just look for which domain the parabola satisfies the inequality. Do enough of these and you'll start recognising these without a sketch.
Original post by Lucofthewoods
If I give two examples please help me I'm slightly confused
For example, (2x+3)(x-1)<0 is -3/2x<x<1 but how do you know it's one inequality and not -3/2<x and 1>x

And then (3x+1)(1-x)<0 why would it be two separate inequalities of x<-3 and x>1?

Also as a third example (3x-2)(2x-1)>or equal to 0 is x<or equal to 1/2 and x>or equal to 2/3


For the first consider (2x+3)(x-1) = 0

We know that the solutions are x = -3/2 or x = 1 so draw a sketch of the graph.

Which part of the graph represents the inequality you want to solve?

I would always suggest drawing a sketch as it is then clear.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you