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# C1 - watch

1. Dear Users,

This might be a simple question, but I have jet to find out the technique.
It is about a C1- Coordinate Geometry Question, basically the beginning of AS level.

I have read the examples, but when I have two points to find the value of unkowns, I find it quiet hard to find the solution when there is one side given but the other side is unknown.

IE.
The line joining (7,2) to (f,3f) has gradient 4. Work out the value of F.
If asked The line is joining (-3,-2) to (2e,5) it is for me able to do.

But as there are two unknowns in one side i find it hard to find these questions;
The line joining (7,2) to (f,3f) has gradient 4. Work out the value of F.
The line joining (3,-4) to (-g,2g) has gradient -3. Work out the value of g.

To be honest I have the answers and they are :
26 and -5 respectively. Please only answer if u mind working it out, in simple layterm questions, please avoid ugly comments I really dont know yet, but when figured I will , thanks oll.
2. Try setting them up in the same way. The process is the same as there is still only one unknown, e.g. g. When you solve this you end up with g=-5.
If you are able to solve the one with e, follow the same process carefully.
3. To work out gradient you do
(y2-y-1/)(x2-x1). So for the first question you have y2-y1=2-3f
And x2-x1= 7-f
Then you now just plug this into the formula for working out gradient - and because the gradient is known to be 4 you should be able to work out what the value of f is.
4. Don't you just plug in everything into the y-y1 =m(x-x1) formula and make the subject f?

For the first question I got 26, which is right. Go over the formula and it should be easy. Just treat f and 3f as normal coordinates.
5. Thanks guys, I managed to find it out.

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Updated: September 13, 2015
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