# Equations:

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• Jul 11th 2007, 05:59 PM
Sazza
Equations:
I'm a bit confused as to where to put this, because as far as i know there's no section for "Equations"
But i've been reading through an introduction to Equations! That's the booklet i have started studying and it has: y + 2 and 5f - 1 are expressions. y and f are called variables. I know all that!
But maybe it's just the case that i've just come off my school holidays, and i'm a bit slow! But i can really remember how to do the following! well i don't really have to do it, i'm not mean't to! Right now it's just stating fact, but when i read i like to be ableto understand what their talking about: y + 2 = 11, and 5f - 1 = 14! i do understand that 5 - 1 is 4! but if it was to live upto the result of 14! it all depends on what the "f" stands for! so in this case would the f stand for 10? But how would y + 2 equal 11??
• Jul 11th 2007, 06:05 PM
Sazza
and i'm totally confused because i'm not used to be doing these things!
Erm, it's just like a quiz to see wheather you can get the number, but i've spend 30 minutes trying to get it! I dare say you can get it!
==============
Think of a number!
1. Half of a number
2. When 4 is added, the result is 12
3. when doubled, the result is 22
4. When 5 is subtracted from it, the result is 3
5. When it is subtracted from 5, the result is 3
6. When squared, the result is 36
7. Add 7 to it, then multiply by 2. The result is 24
8. a quarter of it is 12.
9. The square route of it is 4
10. Add half of it to 11 to give 15
• Jul 11th 2007, 06:28 PM
Jonboy
Hi Sazza! I'm glad that you have an interest. I will most gladly explain these basic equations for you. :)

So the first one is: $y\,+\,2\,=\,11$

This means that some number plus 2 is 11. Just by looking at it I see y = 9.
But you can find y another way until you get skilled.

When solving for a variable in a simple equation, you want to get y = something. So we want to get rid of the 2. Since the 2 is positive, we subtract it from both sides, called the inverse. That's how you solve for a variable. Do the inverse(s )to the term(s) you are trying to get rid of, resulting in getting the variable by itself.

Inverse of multiplication is division
Inverse of addition is subtraction
Inverse of a square is square root
There are many others
• Jul 11th 2007, 06:34 PM
Jonboy
So now we have a little more complication problem with $5f\,-\,1\,=\,14$

So 5 times a number minus 1 is equal to 15.

So we want to get rid of the -1 and the coefficient 5 of f. So the 1 is negative so add it to both sides of the equation getting rid of it.

Now we have: $5f\,=\,15$

We can either say, what times 5 (f) gives me 15? 3

Or we could see 5f is 5 times f. We need to get rid of 5, so we do the inverse, division of both sides of equation by 5.

That get rid of the 5, getting us: $f\,=\,\frac{15}{5}\,=\,3$

Does this make sense?
• Jul 15th 2007, 07:33 PM
Sazza
Quote:

Originally Posted by Jonboy
Does this make sense?

Yes thanks =] but i'm kinda confused here:
i'm totally confused because i'm not used to be doing these things!
Erm, it's just like a quiz to see wheather you can get the number, but i've spend 30 minutes trying to get it! I dare say you can get it!
==============
Think of a number!
1. Half of a number
2. When 4 is added, the result is 12
3. when doubled, the result is 22
4. When 5 is subtracted from it, the result is 3
5. When it is subtracted from 5, the result is 3
6. When squared, the result is 36
7. Add 7 to it, then multiply by 2. The result is 24
8. a quarter of it is 12.
9. The square route of it is 4
10. Add half of it to 11 to give 15
• Jul 15th 2007, 08:08 PM
Jonboy
Well do some practice. I think you'll find this explanation helpful and it has practice problems: Purplemath
• Jul 15th 2007, 08:18 PM
Jhevon
I'll do the first 5, see if you can figure out the rest from what i did
Quote:

Originally Posted by Sazza

Yes thanks =] but i'm kinda confused here:
i'm totally confused because i'm not used to be doing these things!
Erm, it's just like a quiz to see wheather you can get the number, but i've spend 30 minutes trying to get it! I dare say you can get it!
==============
Think of a number!

Okay, let me call the number x

Quote:

1. Half of a number
more info needed here. as far as we know, we just have x/2

Quote:

2. When 4 is added, the result is 12
okay, so x + 4 = 12

=> x = 8 here

Quote:

3. when doubled, the result is 22
2x = 22
=> x = 11 here

Quote:

4. When 5 is subtracted from it, the result is 3
x - 5 = 3

=> x = 8 here

Quote:

5. When it is subtracted from 5, the result is 3
this is the same as the last

• Jul 15th 2007, 11:18 PM
red_dog
5. $5-x=3\Rightarrow x=2$
6. $x^2=36\Rightarrow x=6$ (Suppose x is a positive integer)
7. $2(x+7)=24\Rightarrow x=5$
8. $\frac{x}{4}=12\Rightarrow x=48$
9. $\sqrt{x}=4\Rightarrow x=16$
10. $\frac{x}{2}+11=15\Rightarrow x=8$
• Jul 16th 2007, 06:04 PM
Sazza
Quote:

Originally Posted by Jhevon
I'll do the first 5, see if you can figure out the rest from what i did

Okay, let me call the number x

more info needed here. as far as we know, we just have x/2

okay, so x + 4 = 12

=> x = 8 here

2x = 22
=> x = 11 here

x - 5 = 3

=> x = 8 here

this is the same as the last

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The first number would be 14, because 7+7= 14, but it doesn't really makes sense when i read it, i mean if you were adding 4 onto that number, wouldn't it be 18? but then i relised the number 14 was what the number was before half was taken away so then it would be 8? thanks for all your help :D
• Jul 16th 2007, 06:09 PM
Sazza
and just a quick comparison and question: the aim is to Simplify the following algebraic fractions:
for example 16x/20 (it's in fraction form like the 16x is over the 20, i have not yet mastered how to do those little diagrams) would i: divide [15 divided by 20 = 8x] or [16 x 20 = 320x] i personally am inclined to believe the divided by sum, because that seems a more logical answer, but i'm just checking! so we divide? because i just rememeber in some you multiply!
and also one more question, that i just want to verify, because i'm kind of slow after the holidays! When were writing the answer we have to put the variables in Alpha Order, and for example a question like this: 15xyz/5yz how would we put the variables?? the answer plus xyyzyz?? or what? Thanks =]
• Jul 16th 2007, 06:54 PM
Jonboy
Sazza can you just simply tell us the problem? Lol I'm lost with all the wordiness.

Is it $\frac{16}{20}x$ ?

If so you should review quotient properties: Link