help!! I can't remember for the life of me how to solve equations ..

[basildonbond]

and ds2 is having a complete meltdown saying he 'just can't do it'

I have (rather irritatedly) pointed out that if he'd told me he had a problem a bit earlier then it would have been easier for me to help him but he doesn't want me to help him really he wants me to do it for him ... thus we have an impasse ..

ds has asperger's and gets 'stuck' on things

can anyone talk me through linear equations so I can guide him - I've got vague memories but more of what not to do ...

examples of his questions are 4x-20 = 2x+16 and 3x+5 = 180-2x and 3(x+7)=9(x-5) and there are loads of them ..argh ... the acronym BIDMAS is coming to mind but can't remember what it means ...

You need to start with getting rid of anything added to the unknown.

If you add something to one side, add it to the other.

So, 4x-20= 2x+ 16
4x-2x = 16+20
2x=36

Then if you divide one side by a number, you have to divide the other by the same number.

So x= 36/2=18.

Bidmas is an order of operation used when doing equations, which include both addition and subtraction, or Multiplication and Division.

This is the order it goes in.

Brackets
Indicies
Division
Multiplication
Addition
Subtraction

Another anagram for this is "bodmas" identical, but the "o" stands for "power of" i.e.

Brackets
power Of
Division
Multiplication
Addition
Subtraction

e.g. When given a simple example:
(56 - X)(Y + 7) where X=6 and Y=3.
You must use bidmas. First solve the brackets, which include addition and subtraction but are exempt from the rule as they are inside the brackets and then multiply the two values.

(56 - 6) x (3 + 7) =
50 x 10 = 500

I'm not sure this applies to the problems you're solving though unless you know the value of x

To get started:

The basic idea is to get all the algebraic numbers on one side - so in your examples you want all the x on one side of the =

And you always do the same thing to both sides of the equation

Using your acronym tells you what order to do it in;
Brackets
Indices
Divide
Multiply
Add
subtract

So in your third example you write each side longer to remove the brackets
Instead of 3(x+7) you write 3x +21

And instead of 9(x -5) you write 9x - 45
You can't divide both sides by anything, and multiplying wont help you, so next you go to addition

Add 45 to both sides

So 9x = 3x + 66

Get the 3x across, and to do that you have to 'remove' it from both sides

9x - 3x = 3x - 3x + 66

6x = 66

thank you :)

now for the joy of trying to get ds to sit down and do it before school tomorrow morning ...

Solving equations is all about balancing - imagine an old fashioned set of weighing scales. In order to keep them balanced (eg equal) you have to do the same to both sides.

BIDMAS or BODMAS isn't really useful to solving equations the order just happens to be the same for the examples above.

Basically if you have brackets you want to expand them. Then you need to 'collect like terms' and end up with all the x's on one side and everhing else on the other. In order to do this you have to do the same to both sides.

In your example 4x - 20 = 2x + 16 you have 4 x's on the left side and 2 on the right hand side, so you want to only have x's on the left. In order to 'get rid' of the x from the right hand side you need to subtract 2x, if you do it to one side you must do it to the other side as well so take 2 x from both sides leaving you
2x - 20= 16

Then you want to get rid of the -20 from the left side so in order to do this you have to add 20 (and of course do this to both sides). Adding 20 to both sides gives you...

2x=-4

Then you need to get to a single x on the left side so you need to divide it (and therefore the other side) by 2.

X=-2

. The key is balancing and doing the same to both sides!

Duh! Clearly 16+20 actually is 36!!!

2x=36
X=18