04 June 2012

FINDTHE STRAIGHT LINE

y = mx + c
where m is gradient (m ialah kecerunan)
and c is where the line passing through the y-axis
(c ialah penggal pada paksi-y)


Example
Find the straight line that passing through P(3, 4) and Q(5, 10).


Solution
Step 1 : Find gradient (Cari Kecerunan)
m = (y2 - y1) / (x2 - x1)
m = (10 - 4) / (5 - 3)
m = 6 / 2
m = 3
So y = 3x + c


Step 2 : Find c (Cari c)
Use P(3, 4) or Q(5, 10) either one (Gunakan samada P atau Q)
Let say  use P(3, 4) ; substitute x = 3 and y = 4 on y = 3x + c
4 = 3(3) + c
4 = 9 + c
c = 4 - 9
c = -5


Answer : y = 3x -5

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