# Straight Line GraphsWatch

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Thread starter 1 year ago
#1
The points P and Q have coordinates (1,-1) and (7/2,1/2) respectively. The line L1 passes through P and Q.
The line L2 is perpendicular to L1 and passes through Q.
a Find an equation for L2 giving your answer in the form ax+by+c=0
b Find the exact length of the line between point Q and origin, O.
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1 year ago
#2
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1 year ago
#3
(Original post by freddiek69)
The points P and Q have coordinates (1,-1) and (7/2,1/2) respectively. The line L1 passes through P and Q.
The line L2 is perpendicular to L1 and passes through Q.
a Find an equation for L2 giving your answer in the form ax+by+c=0
b Find the exact length of the line between point Q and origin, O.
(a) First you need the get the gradient of L2. To do that, you need the gradient of L1 since they're perpendicular. To get the gradient of L1, use the fact that it passes through two points you're told. The rest is just making your line go through Q.

(b) Just do the usual Pythagoras approach here for the distance between two points.
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