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## GCSE straight line graph help needed!

This is a discussion on GCSE straight line graph help needed! within the General Off Topic+ forums, part of the QJ.net Forum Miscellaneous category; Argh i feel stupid lol, searched google couldn't find anyhting. Ok so im doing higher gcse maths and im stuck ...

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1. ## GCSE straight line graph help needed!

Argh i feel stupid lol, searched google couldn't find anyhting. Ok so im doing higher gcse maths and im stuck on this simple question:

I have to find out the gradient of a line using two co-ordiantes. The exact question is as follows

Given that the points P(7,4), Q(9,-2),R(-5,-20) and S(-3,4), show by the means of gradients that PR is perpendicular to QS.

Now i cant just write the answer i need the working, the answer is in the back of my book but i cant copy it and i cant figure it out even with the answer.

Basically all i would want would be the gradient of qs and pr, preferably with the explanation. PLease help this is due tomorrow!!! thanks

2. Gradient = Rise / Run = (Y2-Y1)/(X2-X1)
For PR (-20 - 4) / (-5 - 7) = -24 / -12 = 2
For QS (4 - -2) / (-3 - 9) = 6 / -12 = -0.5

If 2 lines are perpendicular, the gradient of one of the lines will be m, the gradient of the other line is (-1/m)
2 = -1/-0.5 therefore they are perpendicular.

Damn...GCSE maths has really gotten easy these days. I remember doing a similar question for my year 9 SATs

3. I really need to revise if I want to do Higher. Its weird I find Intermediate absolutely easy, and Higher absolutely hard. I guess I just got to get down to some good old revision.

http://www.bbc.co.uk/schools/gcsebitesize/ for the win!

4. Originally Posted by muratcan
I really need to revise if I want to do Higher. Its weird I find Intermediate absolutely easy, and Higher absolutely hard. I guess I just got to get down to some good old revision.

http://www.bbc.co.uk/schools/gcsebitesize/ for the win!
i thought it was (in Scotland anyway):
Intermedite 1 & 2 -- Working up to higher
Higher
So you should find higher harder
As you can see i'll pass credit english

5. Lol thanks this is great =] my teacher explained it today but she has the effect of lowering my attention span so i ended up soeaking about the facehuggers off alien instead.. damn they're scary

thansk everyone

6. Rise and Run? I know it as the formula for slope..M = change in y over change in x. Whatever, problem is already answered..so i'm not gonna do it.

Also..perpindicular lines have negative reciprocal slopes..gah i should shut up. Sometimes it's hard for me to shut up..sorry. And..erm..gradient is referred to as slope here.

7. I'd have answered this if I'd known that 'gradient' and 'slope' are the same thing

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