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1. I can't seem to get this question right:
The co-ordinates are : ( 1/2 , - 1/2 ) and gradient is 5/2

I substitute the values in the line equation and should get:
10x - 4y - 7 =0 but I dont

-----------------------------

y + 1/2 = 5/2 ( x - 1/2 )

Multiply through by 2 from the left to give:
2y + 1 = 5 ( 2x - 1 )

I get 5 as 10/2 is 5, and -2/2 is -1 ?

So 2y+1 = 10x -5
2. (Original post by Gelato)
I can't seem to get this question right:
The co-ordinates are : ( 1/2 , - 1/2 ) and gradient is 5/2

I substitute the values in the line equation and should get:
10x ? 4y ? 7 =0 but I dont

-----------------------------

y + 1/2 = 5/2 ( x - 1/2 )

Multiply through by 2 from the left to give:
2y + 1 = 5 ( 2x - 1 )

I get 5 as 10/2 is 5, and -2/2 is -1 ?

So 2y+1 = 10x -5
youdidnt multiply by the -1/2 as well
3. (Original post by hazbaz)
youdidnt multiply by the -1/2 as well
Doesn't that go away if I multiplied it by 2 ? It'll give -1 ?
4. y + 1/2 = 5/2 ( x - 1/2 )

^ The line after this should be:

2y + 1 = 5(x - 1/2)

What you did was multiply the RHS by 4.
5. You need to realise that if you expand [ 5/2 ( 2x - 1) ] , you get TWO terms and not THREE terms.You have multiplied 2 with all three numbers whereas infact there are two [ 5x/2 and 5/4]

Simple.Expand the brackets-

y + 0.5 = 2.5 ( x - 0.5 )

y + 0.5 = 2.5x - 1.25

2.5x - y = 0.5 + 1.25

2.5x - y = 1.75

Multiply throughout by 4.
6. (Original post by electriic_ink)
y + 1/2 = 5/2 ( x - 1/2 )

^ The line after this should be:

2y + 1 = 5(x - 1/2)

What you did was multiply the RHS by 4.
Oh so when I multiply the rhs by 2, only the stuff outside the bracket gets multiplied ?
7. (Original post by Gelato)
Oh so when I multiply the rhs by 2, only the stuff outside the bracket gets multiplied ?
Yes (or you could multiply the stuff inside the bracket). I suppose the best way to explain it is to multiply out the bracket:

=
=
= (the same as multiplying what's outside the bracket).
= (the same as multiplying what's inside the bracket).

8. You use

Substitute the values in to get:

The left side can be converted to a sum as a negative and a negative make a positive:

When you multiply out the right hand side you get:

Take off both sides:

Now get rid of the fractions, so multiply everything by 2:

And then again multiply by 2:

Then put everything on one side:

The only reason I went through it so many steps is for you to understand how to do it, I know I shouldn't really be showing you how to do it straight away but it looks like the other guys have already helped you out enough for me to show you how I would do it. Also, when I was getting rid of the fractions, I understand I couldn't multiplied everything by 4 straight off the bat, however I wanted to show you exactly the steps that were taking place to make it easier.

Hope that helped =D

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Updated: December 21, 2010
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