document.write( "Question 174686: how do i solve the quadratic equasion x^2+11x-80=0 \n" ); document.write( "
Algebra.Com's Answer #129733 by josmiceli(19441)\"\" \"About 
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I like to use the method called \"completing the square\"
\n" ); document.write( "To do this you first get the constant term on the
\n" ); document.write( "other side
\n" ); document.write( "(1) Add \"80\" to both sides
\n" ); document.write( "\"x%5E2+%2B+11x+-+80+=+0\"
\n" ); document.write( "\"x%5E2+%2B+11x+=+80\"
\n" ); document.write( "(2) Now divide the coefficient of the x term by \"2\",
\n" ); document.write( "then square it and add this to both sides
\n" ); document.write( "\"x%5E2+%2B+11x+%2B+%2811%2F2%29%5E2+=+80+%2B+%2811%2F2%29%5E2\"
\n" ); document.write( "The purpose of this is to make the left side a perfect
\n" ); document.write( "square, which it is. It might be hard to see, but I
\n" ); document.write( "can rewrite this as
\n" ); document.write( "\"%28x+%2B+11%2F2%29%5E2+=+80+%2B+%2811%2F2%29%5E2\"
\n" ); document.write( "Now I want to express \"80\" as \"320%2F4\"
\n" ); document.write( "\"%28x+%2B+11%2F2%29%5E2+=+320%2F4+%2B+121%2F4\"
\n" ); document.write( "\"%28x+%2B+11%2F2%29%5E2+=+441%2F4\"
\n" ); document.write( "Now take the square root of both sides
\n" ); document.write( "\"x+%2B+11%2F2+=+0+%2B-sqrt%28441%29%2F2\"
\n" ); document.write( "\"x+=+%28-11+%2B+21%29%2F2\"
\n" ); document.write( "\"x+=+5\"
\n" ); document.write( "and
\n" ); document.write( "\"x+=+%28-11+-+21%29%2F2\"
\n" ); document.write( "\"x+=+-16\"
\n" ); document.write( "check answers:
\n" ); document.write( "\"x%5E2+%2B+11x+-+80+=+0\"
\n" ); document.write( "\"5%5E2+%2B+11%2A5+-+80+=+0\"
\n" ); document.write( "\"25+%2B+55+-+80+=+0\"
\n" ); document.write( "\"0+=+0\"
\n" ); document.write( "OK
\n" ); document.write( "\"%28-16%29%5E2+%2B+11%2A%28-16%29+-+80+=+0\"
\n" ); document.write( "\"256+-+176+-+80+=+0\"
\n" ); document.write( "\"256+-+256+=+0\"
\n" ); document.write( "\"0+=+0\"
\n" ); document.write( "OK\r
\n" ); document.write( "\n" ); document.write( "
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