document.write( "Question 122099: What is the radius and center of a circle with the equation x^2+y^2=100?
\n" ); document.write( "What is the radius and center of a circle with the equation (x-4)^2+y^2=25?
\n" ); document.write( "What is the radius and center of a circle with the equation (x+5)^2+(y-3)^2=18?
\n" ); document.write( "What is the radius and center of a circle with the equation x^2+y^2+4*x-2*y=4?
\n" ); document.write( "What is the radius and center of a circle with the equation x^2+y^2=2*x+10*y+25=0?
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Algebra.Com's Answer #89650 by solver91311(24713) $\"\"$ $\"About$

You can put this solution on YOUR website!


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document.write( "The equation of a circle with center at (h,k) and radius r is:\r
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document.write( "In your first example, you could re-write the equation as\r
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document.write( "Therefore h = 0 and k = 0 so the center is at (0,0) and the radius is 10\r
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document.write( "The second example is a trivial application of what I just showed you,
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document.write( "so you can do that one yourself.\r
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document.write( "The third one has the slight twist that , so \r
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document.write( "The fourth one is a bit trickier.  You need to complete the square for each of the variables\r
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document.write( "First rearrange:\r
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document.write( "Now, what constant, p, do you need to add so that  is a perfect
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document.write( "square?  Let's try 4.  .  So add 4 to both sides of
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document.write( "the equation.\r
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document.write( "Next, look at the y terms.  If we add 1, , so add 1 to
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document.write( "both sides of the equation.\r
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document.write( "Collect terms on the right, and factor the x and y parts of the left\r
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document.write( "Remember the minus signs in the standard circle equation, 
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document.write( "That means we need to re-write the x part:\r
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document.write( "Now we have the circle's parameters directly:  Center at (-2,1), radius = 3\r
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document.write( "Using the process I just showed you for the fourth example, you should be able
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document.write( "to solve the fifth one as soon as you determine whether the equal sign between
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document.write( "the  and  terms should be a plus sign or a minus sign.\r
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document.write( "(Did you hit the adjacent key or forget to shift?)\r
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document.write( "Hope that helps,
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document.write( "John
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