document.write( "Question 389589: Find the X-intercept of the parabola with vertex (-1,-108) and y-intercept of (0,-105). \n" ); document.write( "
Algebra.Com's Answer #276097 by Edwin McCravy(20059)\"\" \"About 
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Find the X-intercept of the parabola with vertex (-1,-108) and y-intercept of (0,-105).
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document.write( "Use the form for the parabola:\r\n" );
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document.write( "y = a(x - h)² + k with vertex (h,k) = (-1,-108)\r\n" );
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document.write( "y = a[x - (-1)]² + (-108) \r\n" );
document.write( "y = a(x + 1)² - 108\r\n" );
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document.write( "Since y-intercept (0,-105) must satisfy the equation\r\n" );
document.write( "we substitute 0 for x any -105 for y:\r\n" );
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document.write( "   y = a(x + 1)² - 108\r\n" );
document.write( "-105 = a(0 + 1)² - 108\r\n" );
document.write( "-105 = a(1)² - 108\r\n" );
document.write( "-105 = a*1 - 108\r\n" );
document.write( "-105 = a - 108\r\n" );
document.write( "   3 = a\r\n" );
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document.write( "So we substitute 3 for a in\r\n" );
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document.write( "y = a(x + 1)² - 108\r\n" );
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document.write( "and get\r\n" );
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document.write( "y = 3(x + 1)² - 108\r\n" );
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document.write( "That's the equation of the parabola\r\n" );
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document.write( "To find the x intercept we substitute 0 for y:\r\n" );
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document.write( "  0 = 3(x + 1)² - 108\r\n" );
document.write( "108 = 3(x + 1)²\r\n" );
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document.write( "Divide both side by 3\r\n" );
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document.write( " 36 = (x + 1)²\r\n" );
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document.write( "Use the principle of square roots:\r\n" );
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document.write( "\"%22%22%2B-+sqrt%28%22%22%29\"36 = x + 1\r\n" );
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document.write( "  ±6 = x + 1\r\n" );
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document.write( "Using the +6\r\n" );
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document.write( "   6 = x + 1\r\n" );
document.write( "   5 = x\r\n" );
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document.write( "Using the -6\r\n" );
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document.write( "  -6 = x + 1\r\n" );
document.write( "  -7 = x\r\n" );
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document.write( "So there are two x-intercepts (5,0) and (-7,0)\r\n" );
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document.write( "\"graph%28500%2C500%2C-10%2C10%2C-150%2C150%2C3%28x%2B1%29%28x%2B1%29+-+108%29\"\r\n" );
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document.write( "Edwin

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