



 
Hi Bob, I agree with your rewriting of the equation x^{2}+y^{2}2x3 = 0 as (x1)^{2}+y^{2}=4 since then it is clear that the equation represents the circle with centre (1,0) and radius 4. This is the green circle in my diagram.
If you then stretched horizontally by a factor of 2 you multiply the xvalues by 2. Thus the centre of the circle (1,0) moves to (2,0), the point (3,0) moves to (6,0) and the point (1,0) moves to (2,0) and I get the orange ellipse. What is its equation? Penny  


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