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 Post subject: Help please - Algebra
PostPosted: Tue Dec 11, 2007 6:38 pm 
Hi

My son is stuck on the following and I can't help !

5h - 5 = 4h + 7

and

7t + 11 = 6t + 3

Please can someone help ?

Many thanks :)


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 Post subject:
PostPosted: Tue Dec 11, 2007 7:09 pm 
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Joined: Tue Dec 13, 2005 12:49 pm
Posts: 1647
Location: berkshire
What you do to one side you must do to the other...the aim is to get all the x's and all the numbers together.


5h - 5 = 4h + 7
5h =4h + 7+ 5 (add 5 to each side)
5h - 4h = 7 + 5 (subtract 4h from each side)
h = 12

7t + 11 = 6t + 3

7t - 6t + 11 = 3 ( subtract 6h from each side)

7t - 6t = 3 -11 (subtract 11 from each side)

t = -8


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PostPosted: Tue Dec 11, 2007 11:44 pm 
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Joined: Fri Jul 06, 2007 8:31 pm
Posts: 1192
Anonymous wrote:
Hi

My son is stuck on the following and I can't help !

5h - 5 = 4h + 7

and

7t + 11 = 6t + 3

Please can someone help ?

Many thanks :)


Imagine some scales. The = is in the middle of the scales.

5h - 5 = 4h + 7

to keep the scales balanced always perform the same operation to both sides

Subtract 4h from both sides

h - 5 = 7

add 5 to both sides

h = 12


and...

7t + 11 = 6t + 3

Subtract 6t from both sides

t + 11 = 3

subtract 11 from both sides

t = -8

Once you get the hang of it you can imagine things moving to the other side and the sign changing...

Regards
SVE

_________________
Animis opibusque parati


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PostPosted: Wed Dec 12, 2007 8:54 am 
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Joined: Thu Oct 11, 2007 11:51 am
Posts: 14
Anonymous wrote:
Hi

My son is stuck on the following and I can't help !

5h - 5 = 4h + 7

and

7t + 11 = 6t + 3

Please can someone help ?

Many thanks :)


If u bring the right hand side h to left hand side,
then 5h-4h-5=7 ,then the equation will become
h-5=7

then

u know h= 5+7=12 after bringing -5 to the right side.

2) 7t+11=6t+3


the same rule,

7t-6t+11=3,

t+11=3,

t=3-11=-8

t=-8. hope this helps


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 Post subject:
PostPosted: Wed Dec 12, 2007 12:39 pm 
Thanks for the replies...

We are getting there slowly,my son has gone from never having done any algebra in the Junior school to this homework.

Please could someone help with this one ?

3x + 5 = 4x - 2

I never did algebra at school so I'm no help to my son at all !

Many thanks.


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 Post subject:
PostPosted: Wed Dec 12, 2007 2:39 pm 
Anonymous wrote:
Thanks for the replies...

We are getting there slowly,my son has gone from never having done any algebra in the Junior school to this homework.

Please could someone help with this one ?

3x + 5 = 4x - 2

I never did algebra at school so I'm no help to my son at all !

Many thanks.


Always do the same thing to both sides of the equals to simplify equation.

Subtract 3x

5=x-2

Add 2

x=7

OR

Subtract 4x

-x+5=-2

Subtract 5

-x=-7

x=7 (essentially adding x and 7 to each side)


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 Post subject: Solving equations
PostPosted: Wed Dec 12, 2007 4:49 pm 
When asked to solve an equation, what it is really asking you to find is the numerical value for x, which when you substitute into both sides of the equation, both sides equal each other.
Ultimately, you have to gather all the unknown terms on one side of the equation and all the numbers on the other. To do this you add/subtract/multiply/divide etc depending on the level of difficulty and "whatever you do to one side you have to do to the other". I have to admit when I introduce this I draw pictures!!!!! and we answer it visually first then set about sorting out the algebra.
so 3x + 5 = 4x - 2 Look at the quantities of x, which is the larger? Ok, then how do you reduce 3x back to zero? well subtract 3x, but "whatever you do to one side you have to do to the other."
(-3x) 5 = x - 2 (-3x)
(+2) 7 = x (+2) the rationale here being "how do you get -2 back to zero? By adding 2.....
Al this sounds very lengthy but I'm attempting to put into words what I say to my teaching groups. Visual, verbal, explaining what you are doing each time in a few examples, then let the students go for it themselves. I always always encourage my students to write in brackets what they are doing.
Hope this helps in a small way. Trying to write what you say when you teach is very very long-winded!!!!! Sorry.
Yours C.
BTW this is how it would look on paper:
3x +5 = 4x - 2
(-3x) 5 = x - 2 (-3x)
(+2) 7 = x (+2)


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 Post subject:
PostPosted: Thu Dec 13, 2007 6:10 am 
Thankyou all very much for your help,the homework is done, he is happy and I am very relieved . This is just the first term of year 7,I dread to think how we will manage in later years !


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 Post subject:
PostPosted: Thu Dec 13, 2007 10:27 am 
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Joined: Mon Feb 20, 2006 1:29 pm
Posts: 1805
Location: Berkshire
Having been taught a different method of doing algebra to the above when I was at school, does anyone know if this is now the standard method used at secondary, or do they progress onto something different?

Thanks

BW


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 Post subject:
PostPosted: Thu Dec 13, 2007 11:51 am 
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Joined: Tue Dec 13, 2005 12:49 pm
Posts: 1647
Location: berkshire
I would recommend the Usborne Dictionary of Maths for any parent with a child in senior school....excellent diagrams, explanations and examples written in a way that I can understand and my son can understand. This has the added benefit of showing the accepted way of approaching the maths curriculum. One of the best £8's I have spent. My son, now in Y8, still uses it if he is not sure of a subject. :D


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