PDA

View Full Version : Can someone explain linear inequalities plainly.


abstractvizual
Nov 17, 2009, 06:46 PM
I have read the book at least 5 times, and gone over the problems but I am just not getting it. It is too confusing. :confused:
Some sample problem from the book were

5(4x-)+3(5-5x)>2(2x+3)-4

-4(4y+2)-(-3y-7)=-3

-1/6(x-12)+1/3(x+3)=x-27

I someone can explain the top one and one of the bottom 2 I would certainly appreciate it. I have a test coming up soon and I can't even get past the chapter work.

Thanks.

Unknown008
Nov 18, 2009, 06:31 AM
5(4x-)+3(5-5x)>2(2x+3)-4

Hmm, I think you missed something after the '4x-'

Anyway, what you have to do:
1. Expand the brackets.
2. Treat the inequality sign as an equal sign; which enables you to add and subtract from both sides, so that you can make all the terms in x on one side, and those without x on the other side.
3. If division or multiplication is required, then be careful about negative numbers. If you multiply or divide everything by a negative value, the sign reverts itself.

To solve the second one,
1. Expand the brackets first.
2. Add, subtract, multiply, divide on both sides to that you have all terms in x on one side and terms without x on the other.

Example:

3x + 12 = 2x - 2

Subtract 12 from both sides, giving:

3x + 12 - 12 = 2x - 2 - 12
3x = 2x - 14

Subtract 2x from both sides:

3x - 2x = 2x - 14 - 2x
x = -14

See? Try all the problems you posted now, and post your answers. :)

morgaine300
Nov 18, 2009, 11:27 PM
It really would be terribly useful if we could see your efforts at solving them, in order to know what you are not understanding. I'm not quite sure if you don't get how to do inequalities specifically, or you just still don't know how to solve problems like these that include distributing, combining like terms, etc. Or even if you're just letting the bigger-looking problems scare you. I just notice that only the first one even is an inequality.

The only real different in doing an inequality is what Unknown008 had in step #3 - that the sign flips when multiplying or dividing by a negative. They are otherwise solved as though there were an equal sign. Since you've included two equalities (rather than inequalities), I wonder if it's something else you don't understand?