# C1Watch

This discussion is closed.
#1
How do you get from
(y-4/3-4) = (x-2/5-2)
which my notes say is the formula for the eqtn of a traight line

to equal x+3y-14=0

its co-ordinate geometry but i dont understand how you get

y-y1/y2-y1 = x-x1/x2-x1 how is this the eqtn of a straight line??
0
14 years ago
#2
can you use brackets please? thanks
I don't understand what the first part means
0
#3
im jus tconfused no the easy stuff - see edited above!!
0
14 years ago
#4
try cross multiplying.
0
14 years ago
#5
(Original post by jonny sss)
How do you get from
(y-4/3-4) = (x-2/5-2)
which my notes say is the formula for the eqtn of a traight line

to equal x+3y-14=0

its co-ordinate geometry but i dont understand how you get

y-y1/y2-y1 = x-x1/x2-x1 how is this the eqtn of a straight line??

equation of a straight line is y-y1=m(x-x1)

m=(y2-y1)/(x2-x1)
so (y-y1)=(y2-y1)/(x2-x1)*(x-x1)
so (y-y1)/(y2-y1)=(x-x1)/(x2-x1)

(y-4)/(3-4) = (x-2)/(5-2)
so (y-4)(3)=-1(x-2)
so 3y-12=-x+2
sp 3y+x-14=0

Just remember to put brackets in to make your working clearer.
0
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