document.write( "Question 565393: A semicircle has a radius of a + 5 and the center is the origin. The point (15, a) lies on the circle. Solve for a. \n" ); document.write( "
Algebra.Com's Answer #365791 by AnlytcPhil(1807)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "[Notice that I changed your letter \"x\" to the letter \"a\" because this problem\r\n" );
document.write( "is about an unknown constant, but \"x\" is a variable.  The problem would be\r\n" );
document.write( "very confusing if we let \"x\" be both an unknown constant and a variable as well.\r\n" );
document.write( "If this problem was given with \"x\" representing an unknown constant,\r\n" );
document.write( "you should point this out to your teacher.]\r\n" );
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document.write( "A semicircle has a radius of a + 5 and the center is the origin. The point (15, a) lies on the circle. Solve for a.\r\n" );
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document.write( "  x² + y² = r²\r\n" );
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document.write( "  x² + y² = (a + 5)²\r\n" );
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document.write( "Substitute in the point (15, a)\r\n" );
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document.write( "15² + a² = (a + 5)²\r\n" );
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document.write( "225 + a² = (a + 5)(a + 5)\r\n" );
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document.write( "225 + a² = a² + 10a + 25\r\n" );
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document.write( "     200 = 10a\r\n" );
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document.write( "      20 = a \r\n" );
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document.write( "So the radius is a + 5 or 20 + 5 or 25, and the point (15,a) is (15,20).\r\n" );
document.write( "and the grpah is this:\r\n" );
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document.write( "Edwin
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