document.write( "Question 582589: Where does the graph of y = 2x^2 − x − 3 cross the x-axis?\r
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\n" ); document.write( "\n" ); document.write( "C. (−, 0) and (1, 0)\r
\n" ); document.write( "\n" ); document.write( "D. (, 0) and (−1, 0)
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Algebra.Com's Answer #372114 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Simply set y equal to zero and solve for x:\r
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\n" ); document.write( "\n" ); document.write( "\"y=2x%5E2-x-3\" Start with the given equation\r
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\n" ); document.write( "\n" ); document.write( "\"0=2x%5E2-x-3\" Plug in y = 0\r
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\n" ); document.write( "\n" ); document.write( "\"2x%5E2-x-3=0\" Flip the equation.\r
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\n" ); document.write( "\n" ); document.write( "Notice that the quadratic \"2x%5E2-x-3\" is in the form of \"Ax%5E2%2BBx%2BC\" where \"A=2\", \"B=-1\", and \"C=-3\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for \"x\":\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29\" Start with the quadratic formula\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Plug in \"A=2\", \"B=-1\", and \"C=-3\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+%28-1%29%5E2-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Negate \"-1\" to get \"1\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+1-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Square \"-1\" to get \"1\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+1--24+%29%29%2F%282%282%29%29\" Multiply \"4%282%29%28-3%29\" to get \"-24\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+1%2B24+%29%29%2F%282%282%29%29\" Rewrite \"sqrt%281--24%29\" as \"sqrt%281%2B24%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+25+%29%29%2F%282%282%29%29\" Add \"1\" to \"24\" to get \"25\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+25+%29%29%2F%284%29\" Multiply \"2\" and \"2\" to get \"4\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+5%29%2F%284%29\" Take the square root of \"25\" to get \"5\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B+5%29%2F%284%29\" or \"x+=+%281+-+5%29%2F%284%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%286%29%2F%284%29\" or \"x+=++%28-4%29%2F%284%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+3%2F2\" or \"x+=+-1\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "So the solutions are \"x+=+3%2F2\" or \"x+=+-1\" \r
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\n" ); document.write( "This means that the x-intercepts are (3/2, 0) and (-1, 0). These are the points where the graph crosses the x-axis.\r
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