document.write( "Question 1087244: If f(x)= 2x^3 - x, find [f(x+h)-f(x)]/h\r
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Algebra.Com's Answer #701517 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
The first thing we need to do is find \"f%28x%2Bh%29\". We do this by replacing every copy of x with x+h\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%29=+2x%5E3+-+x\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%29=+2%28x%29%5E3+-+%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28highlight%28x%29%29=+2%28highlight%28x%29%29%5E3+-+%28highlight%28x%29%29\" Highlighting the x terms we will replace\r
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\n" ); document.write( "\n" ); document.write( "\"f%28highlight%28x%2Bh%29%29=+2%28highlight%28x%2Bh%29%29%5E3+-+%28highlight%28x%2Bh%29%29\" Replacing those terms with x+h\r
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\n" ); document.write( "\n" ); document.write( "So we have\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+2%28x%2Bh%29%5E3+-+%28x%2Bh%29\"\r
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\n" ); document.write( "\n" ); document.write( "Let's expand that out and simplify\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+2%28x%2Bh%29%2A%28x%2Bh%29%5E2+-+%28x%2Bh%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+%28x%2Bh%29%282%2A%28x%2Bh%29%5E2+-+1%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+%28x%2Bh%29%282%2A%28x%5E2%2B2xh%2Bh%5E2%29+-+1%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+%28x%2Bh%29%282x%5E2%2B4xh%2B2h%5E2+-+1%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+x%282x%5E2%2B4xh%2B2h%5E2+-+1%29%2Bh%282x%5E2%2B4xh%2B2h%5E2+-+1%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+2x%5E3%2B4x%5E2h%2B2h%5E2x+-+x%2B2x%5E2h%2B4xh%5E2%2B2h%5E3+-+h\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+2x%5E3%2B4x%5E2h%2B2x%5E2h%2B2h%5E2x%2B4xh%5E2+-+x%2B2h%5E3+-+h\"\r
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\n" ); document.write( "\n" ); document.write( "\"f%28x%2Bh%29=+2x%5E3%2B6x%5E2h%2B6xh%5E2+-+x%2B2h%5E3+-+h\"\r
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\n" ); document.write( "\n" ); document.write( "Now we can compute the difference quotient\r
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\n" ); document.write( "\n" ); document.write( "\"%28f%28x%2Bh%29-f%28x%29%29%2Fh+=+%286x%5E2h%2B6xh%5E2%2B2h%5E3+-+h%29%2Fh\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28f%28x%2Bh%29-f%28x%29%29%2Fh+=+%28h%286x%5E2%2B6xh%2B2h%5E2+-+1%29%29%2Fh\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28f%28x%2Bh%29-f%28x%29%29%2Fh+=+6x%5E2%2B6xh%2B2h%5E2+-+1\"\r
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\n" ); document.write( "\n" ); document.write( "So the final answer is \"%28f%28x%2Bh%29-f%28x%29%29%2Fh+=+6x%5E2%2B6xh%2B2h%5E2+-+1\"\r
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\n" ); document.write( "\n" ); document.write( "Side Note: After this step is reached, you can plug in h = 0 to find the derivative of f(x). This topic probably hasn't come up yet in your course, but it definitely will come up in calculus.
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