document.write( "Question 117519:
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Algebra.Com's Answer #86024 by bucky(2189)\"\" \"About 
You can put this solution on YOUR website!
Let's actually make such an equation ... one that has has 3 factors that are roots with two of the
\n" ); document.write( "factors being equal. We can, for example establish the equation:
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\n" ); document.write( "\"f%28x%29+=+%28x+%2B+3%29%2A%28x+-+4%29%2A%28x-4%29\"
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\n" ); document.write( "You can multiply out these factors to get the cubic equation they form. First multiply the
\n" ); document.write( "two factors identical factors to get that product:
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\n" ); document.write( "\"%28x+-+4%29%2A%28x+-+4%29+=+x%5E2+-+8x+%2B+16\"
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\n" ); document.write( "Multiply this product by the third factor \"x+%2B+3\". Without going through all the work, this
\n" ); document.write( "multiplication results in:
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\n" ); document.write( "\"f%28x%29+=+x%5E3-5x%5E2+-8x+%2B+48\"
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\n" ); document.write( "The graph of this cubic equation is:
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\n" ); document.write( "\"graph+%28400%2C+400%2C+-10%2C+10%2C+-70%2C+70%2C++x%5E3+-+5x%5E2+-+8x+%2B+48%29\"
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\n" ); document.write( "Note what this graph tells you. The function was built using (x + 3) as one of the factors. Notice
\n" ); document.write( "that this factor results in the graph crossing the x-axis at x equal to -3. The two (x – 4) factors
\n" ); document.write( "cause the graph to be just tangent to the x-axis where x equals +4. So this graph illustrates a
\n" ); document.write( "cubic function that has one root that is singular and has a pair of identical roots.
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\n" ); document.write( "You can convert this function to one having three separate real roots by shifting the function
\n" ); document.write( "down an appropriate amount. Suppose we start with:
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\n" ); document.write( "\"f%28x%29+=+x%5E3+-+5x%5E2+-+8x+%2B+48\"
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\n" ); document.write( "and subtract 25 from both sides. When you do that, the equation becomes:
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\n" ); document.write( "\"f%28x%29+-+25+=+x%5E3+-+5x%5E2+-+8x+%2B+23\"
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\n" ); document.write( "and the corresponding graph is:
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\n" ); document.write( "\"graph+%28400%2C+400%2C+-10%2C+10%2C+-70%2C+70%2C+x%5E3+-+5x%5E2+-+8x+%2B+23%29\"
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\n" ); document.write( "The graph shows now that there are three separate roots for this function. The roots are real, and
\n" ); document.write( "because they are at different places on the x-axis, they are unequal roots.
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\n" ); document.write( "For part b of this problem, the opposite is done. Instead of subtracting 25 from both sides
\n" ); document.write( "of the original function, add 10 to both sides of the original function to raise the graph
\n" ); document.write( "so that the point of tangency in the original graph is raised. Adding 10 to both sides results in:
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\n" ); document.write( "\"f%28x%29+%2B+10+=+x%5E3+-+5x%5E2+-+8x+%2B+58\"
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\n" ); document.write( "and the graph of this is the same as the original graph ... just shifted upward:
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\n" ); document.write( "\"graph%28400%2C+400%2C+-10%2C+10%2C+-70%2C+70%2C+x%5E3+-+5x%5E2+-+8x+%2B+58%29\"
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\n" ); document.write( "As a result the graph crosses or touches the x-axis at one point. This means that there is
\n" ); document.write( "one real root (established by the x-axis crossing) and two complex roots (having an imaginary parts)
\n" ); document.write( "to comprise the three roots of the cubic function.
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\n" ); document.write( "Hope that this helps you to understand what the problem was asking for, how to do it, and
\n" ); document.write( "what the results mean.
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