Im tearing my hair out! Who is strong in algebra?

stellie • 5 February 2013 at 5:10 PM

This inequality equation:

-2x+4_>20

(its supposed to be equal/greater than symbol)

and this 3x+2>8 and how do you graph it on a numberline?

Please explain, Im an A+ student in algebra but this stumps me for some reason >.<

rebel • 5 February 2013 at 5:16 PM

@stellie Oh cool we just finished inequalities! 😊 Do you know how to simplify them?

hai • 5 February 2013 at 5:18 PM

@stellie

-2x+4 is greater than or equal to 20
-2x is greater than or equal to 16
x is less than or equal to(going <) -8

3x+2>8 will have an open circle with the highlighted part going >

lucky_cricket • 5 February 2013 at 5:19 PM

@stellie treat them like normal solving questions, just solve for x. The sign in the middle doesn't matter. I can give you the answers if you want, but if you think of it as a normal solving question, then it should be fine.

One thing you must remember, if you are dividing or multiplying each side by a negative, flip the sign in the middle.

Ex:

-x>2 = x<-2

stellie • 5 February 2013 at 5:24 PM

@lucky_cricket I got x=-8 now what? thanks tho!

@hai can you explain it baby talk? Im sorry >.<

@rebel Im having trouble with that ☹️

hai • 5 February 2013 at 5:29 PM

@stellie

Just solve the inequalities like any normal equation. But since you divide by a negative you would flip the sign.

The second one seems simple enough.

stellie • 5 February 2013 at 5:33 PM

@hai

I solved the 1st and got -8 for x thats right and now checking is confusing, I started out like this:

-2(-8)+4>_20
16+4>_20
20=20

Seems legit?

the second I got x=2+

hai • 5 February 2013 at 5:35 PM

@stellie

The check is right as 20=20 and the first equation has greater than or EQUAL to 20.

stellie • 5 February 2013 at 5:37 PM

@hai


Okay, I get that one, now with negatives, i heard that when there is a negative, you divide/multiply it 1 to get the final answer, what in the world does that mean?

twilight_raptor • 5 February 2013 at 5:38 PM

You seem to have got the first one right x _> -8
x can be -8 or any number greater than it.


2)

3x+2>8
3x > 8-2
3x > 6
x > 6/3
x > 2

Therefore on the number line it x would occupy numbers greater than 2 but not equal to it.

whitefall • 5 February 2013 at 5:41 PM

@stellie

-2x + 4 _> 20
-2x _> 16
x <_ -8

3x + 2 > 8
3x > 6
x > 6

So you would draw an open circle at 2 and make the ray go the the right of the number.

[-----|-----o__________>]
0. 1. 2. 3. 4

O_______> is my fail ray.

stellie • 5 February 2013 at 5:44 PM

@whitefall

Thanks!

whitefall • 5 February 2013 at 5:46 PM

@stellie
I just drew the number line diagram too

stellie • 5 February 2013 at 6:04 PM

@whitefall

very helpful you can be a math teacher!

lucky_cricket • 5 February 2013 at 6:27 PM

@stellie x=-8 is a fine answer, don,t doubt yourself!! You can also check by plugging -8 back into the equation.

Sometimes you may get weird answers, on my math exam on an inequalities question I got -17/11 for my final answer. It looked weird to me, but it turns out it was right 😊

Negatives or fractions in your answers are fine, as long as in the answer section of your work, the answer comes out to something like this: x=2, -x=-2 is not correct, as your "x" in question always has to be positive.

Meteoroid • 8 February 2013 at 1:45 PM

Topic moved to appropriate section.

dreamer • 8 February 2013 at 1:55 PM

@Stellie I know it's late, but I think I remember the whole line diagram thing. We went over it very briefly this year in PreAlgebra, so I'm a bit rusty, but I think I understand the inequality thing.

Obviously, X is the variable. In an inequality, X counts for every number. You don't have to solve X, but you can use a few numbers for example.

Choose your x, then multiply it by -2. Then add 4 to that.

Let's say I chose x=8:

-2x8+4=-12

That's less than 20.

Yet at the same time, x could be -8 (which would be equal to 20), or -9 (which would be more than 20)...

Bleh. I'm awful with math help. XD I'll have to review this lesson, since I don't remember anything except for how to graph it on a numberline.