document.write( "Question 180326: Can you please help me solve this problem?!!? \"9x%5E4=25x%5E2-16\"
\n" ); document.write( "The directions say: solve the equation by making the appropriate substitution.
\n" ); document.write( "Here is what I have so far....but I am stuck.\r
\n" ); document.write( "\n" ); document.write( "\"9x%5E4-25x%5E2%2B16=0\"
\n" ); document.write( "\"%283x%5E2%29%5E2-25x%5E2%2B16=0\"
\n" ); document.write( "\"3u%5E2-25u%2B16=0\"\r
\n" ); document.write( "\n" ); document.write( "At this point I wasn't sure. Do I use the quadratic formula??? I tried that but just got confused. Please help. Thanks.
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Algebra.Com's Answer #135150 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
\"9x%5E4-25x%5E2%2B16=0\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "Let \"u=x%5E2\". This means that \"u%5E2=x%5E4\"\r
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\n" ); document.write( "\n" ); document.write( "\"9u%5E2-25u%2B16=0\" Replace \"x%5E4\" with \"u%5E2\" and \"x%5E2\" with \"u\"\r
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\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic equation in the form of \"au%5E2%2Bbu%2Bc\" where \"a=9\", \"b=-25\", and \"c=16\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for u\r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%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( "\"u+=+%28-%28-25%29+%2B-+sqrt%28+%28-25%29%5E2-4%289%29%2816%29+%29%29%2F%282%289%29%29\" Plug in \"a=9\", \"b=-25\", and \"c=16\"\r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+sqrt%28+%28-25%29%5E2-4%289%29%2816%29+%29%29%2F%282%289%29%29\" Negate \"-25\" to get \"25\". \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+sqrt%28+625-4%289%29%2816%29+%29%29%2F%282%289%29%29\" Square \"-25\" to get \"625\". \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+sqrt%28+625-576+%29%29%2F%282%289%29%29\" Multiply \"4%289%29%2816%29\" to get \"576\"\r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+sqrt%28+49+%29%29%2F%282%289%29%29\" Subtract \"576\" from \"625\" to get \"49\"\r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+sqrt%28+49+%29%29%2F%2818%29\" Multiply \"2\" and \"9\" to get \"18\". \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B-+7%29%2F%2818%29\" Take the square root of \"49\" to get \"7\". \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2825+%2B+7%29%2F%2818%29\" or \"u+=+%2825+-+7%29%2F%2818%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+%2832%29%2F%2818%29\" or \"u+=++%2818%29%2F%2818%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"u+=+16%2F9\" or \"u+=+1\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "Now remember, we let \"u=x%5E2\", so this means that \r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2+=+16%2F9\" or \"x%5E2+=+1\"\r
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\n" ); document.write( "\n" ); document.write( "Let's solve the first equation \"x%5E2+=+16%2F9\":\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+0%2B-sqrt%2816%2F9%29\" Take the square root of both sides\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+sqrt%2816%2F9%29\" or \"x+=+-sqrt%2816%2F9%29\" Break up the \"plus/minus\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+4%2F3\" or \"x+=+-4%2F3\" Take the square root of \"16%2F9\" to get \"4%2F3\"\r
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\n" ); document.write( "\n" ); document.write( "So the first two solutions are \"x+=+4%2F3\" or \"x+=+-4%2F3\"\r
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\n" ); document.write( "\n" ); document.write( "Now let's solve the second equation \"x%5E2+=+1\":\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+0%2B-sqrt%281%29\" Take the square root of both sides\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+sqrt%281%29\" or \"x+=+-sqrt%281%29\" Break up the \"plus/minus\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+1\" or \"x+=+-1\" Take the square root of \"1\" to get \"1\"\r
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\n" ); document.write( "\n" ); document.write( "So the next two solutions are \"x+=+1\" or \"x+=+-1\"\r
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\n" ); document.write( "\n" ); document.write( "Answer:\r
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\n" ); document.write( "\n" ); document.write( "So the 4 solutions are:\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+4%2F3\", \"x+=+-4%2F3\", \"x+=+1\" or \"x+=+-1\"
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