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Question 3566: How do i determine the equation of this line: parallel to the line -2x+3, containing the point(-2,1)?
Answer by Pieter(35)   (Show Source):
You can put this solution on YOUR website! if you know that the general equation for a circle with midpoint M(a,b) is
(x-a)²+(y-b)²= r², you can work this equation out:
x² - 2ax + a² + y² - 2by + b² - r² = 0
if you compare this with x² + 4x + y² - 5 = 0,
you can conclude that b = 0 (the y coordinate from the midpoint),
and - 2a = 4 or a = -2
then we still have a² - r² = -5
-r² = -5 - 4 = -9 or r² = 9 so r = 3
So your circle has midpoint M(-2,0) and radius r=3
i hope you understand the reasoning,
otherwise contact me
Greets
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