document.write( "Question 963221: Find the cubic wquation that has -1 adn 2i as roots. Choices
\n" ); document.write( "a)y=x cubed - x squared + 4x - 4
\n" ); document.write( "b)y=x cubed + x squared - 4x - 4
\n" ); document.write( "c)y=x cubed + x squared + 4x + 1
\n" ); document.write( "d)y=x cubed + x squared + 4x + 4
\n" ); document.write( "e)y=x cubed - x squared + 4x - 1\r
\n" ); document.write( "\n" ); document.write( "The book says the answer is D, but I do not understand the steps to get there.
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Algebra.Com's Answer #588457 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "the cubic equation that has \"x%5B1%5D=-1\" and \"x%5B2%5D=2i\" as roots, have also \"x%5B3%5D=-2i\" because complex root come always in pairs\r
\n" ); document.write( "\n" ); document.write( "now, since we have all roots, we can use zero product rule to see which cubic equation is right answer\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x-x%5B1%5D%29%28x-x%5B2%5D%29%28x-x%5B3%5D%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x-%28-1%29%29%28x-2i%29%28x-%28-2i%29%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x-2i%29%28x%2B2i%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x%5E2-%282i%29%5E2%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x%5E2-%284i%5E2%29%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x%5E2-%284%28-1%29%29%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x%5E2-%28-4%29%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=%28x%2B1%29%28x%5E2%2B4%29\"\r
\n" ); document.write( "\n" ); document.write( "\"y=x%5E3%2B4x%2Bx%5E2%2B4\"\r
\n" ); document.write( "\n" ); document.write( "\"y=x%5E3%2Bx%5E2%2B4x%2B4\"....=> so, answer is \"D\"\r
\n" ); document.write( "\n" ); document.write( "or, you can do it this way:\r
\n" ); document.write( "\n" ); document.write( "\"y=x%5E3%2B+x%5E2+%2B+4x+%2B+4\"....to find zeros, set \"y=0\" and factor completely\r
\n" ); document.write( "\n" ); document.write( "\"0=%28x%5E3%2B+4x%29%2B+%28x%5E2++%2B+4%29\"\r
\n" ); document.write( "\n" ); document.write( "\"0=x%28x%5E2%2B+4%29%2B+%28x%5E2++%2B+4%29\"\r
\n" ); document.write( "\n" ); document.write( "\"%28x%2B+1%29+%28x%5E2++%2B+4%29=0\"\r
\n" ); document.write( "\n" ); document.write( "solutions:\r
\n" ); document.write( "\n" ); document.write( "if \"%28x%2B+1%29\" => \"x=-1\"
\n" ); document.write( "if \"%28x%5E2++%2B+4%29=0\" => \"x%5E2+=-+4\"=>\"x=sqrt%28-4%29\"=>\"x=2i\" or \"x=-2i\"\r
\n" ); document.write( "\n" ); document.write( "=> one more time we got that answer is \"D\"\r
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