# Math Help - Circle???

1. ## Circle???

the circle X^2+y^2-2x-3=0 is stretched horizontally by a factor of 2 to obtain an ellipse what is the equaion of this ellipse in genral form

okay i dont get it!

2. Originally Posted by andrew93
the circle X^2+y^2-2x-3=0 is stretched horizontally by a factor of 2 to obtain an ellipse what is the equaion of this ellipse in genral form

okay i dont get it!
Find the standard form,
$(x^2-2x+1)+y^2=4$
$(x-1)^2+y^2=4$
Thus a circle of radius 2 centered at (1,0)

Pretend you have a regular circle of radius 2 and you stech the horizontal by factor of 2 what happends? The ellipse will have a horizontal axis of 4 and vertical axis of 2. The the semi-horizontal and semi-vertical axes, respectively, are. 2,1. In that case the equation of the ellipse is,
$\frac{(x-1)^2}{2^2}+\frac{y^2}{1^2}=1$