From Förberedande kurs i matematik 1

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	If we write the equation as		If we write the equation as
		+	{{Displayed math||<math>(x-0)^2 + (y-0)^2 = 9</math>}}
-	<math>\left( x-0 \right)^{2}+\left( y-0 \right)^{2}=9</math>	+	we can interpret the left-hand side as the square of the distance between the points (''x'',''y'') and (0,0). The whole equation says that the distance from a point (''x'',''y'') to the origin should be constant and equal to <math>\sqrt{9}=3\,</math>, which describes a circle with its centre at the origin and radius 3.
-	we can interpret the left-hand side as the square of the distance between the points
-	<math>\left( x \right.,\left. y \right)</math>
-	and
-	<math>\left( 0 \right.,\left. 0 \right)</math>.
-	The whole equation says that the distance from a point (
-	<math>\left( x \right.,\left. y \right)</math>
-	to the origin should be constant and equal to
-	<math>\sqrt{9}=3</math>, which describes a circle with its centre at the origin and radius
-	<math>\text{3}</math>.
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	<center> [[Image:4_1_6_a.gif]] </center>		<center> [[Image:4_1_6_a.gif]] </center>
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-	{{NAVCONTENT_STOP}}

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Current revision

If we write the equation as

\displaystyle (x-0)^2 + (y-0)^2 = 9

we can interpret the left-hand side as the square of the distance between the points (x,y) and (0,0). The whole equation says that the distance from a point (x,y) to the origin should be constant and equal to \displaystyle \sqrt{9}=3\,, which describes a circle with its centre at the origin and radius 3.