document.write( "Question 27864: Find all positie values for K for which each of the following can be factored.\r
\n" ); document.write( "\n" ); document.write( "x^2 + x - k\r
\n" ); document.write( "\n" ); document.write( "Thank you for your help.
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Algebra.Com's Answer #15179 by bmauger(101)\"\" \"About 
You can put this solution on YOUR website!
It can only be factored if the discriminant is positive and a perfect square. The discriminant is defined by:
\n" ); document.write( "\"b%5E2-4ac\" for \"ax%5E2%2Bbx%2Bc\"
\n" ); document.write( "For your problem \"x%5E2+%2B+x+-+k\" a=1, b=1 and c=-k
\n" ); document.write( "so the descriminant is \"1%2B4k\"
\n" ); document.write( "So any number that when multiplied by 4 is one less than a square number would work. Such as:
\n" ); document.write( "0 --> 1+4*0=1 --> \"x%5E2%2Bx=%28x%2B1%29%28x%29\"
\n" ); document.write( "2 --> 1+4*2=9 --> \"x%5E2%2Bx-2=%28x%2B2%29%28x-1%29\"
\n" ); document.write( "6 --> 1+4*6=25 --> \"x%5E2%2Bx-6=%28x%2B3%29%28x-2%29\"
\n" ); document.write( "12 --> 1+4*12=49 --> \"x%5E2%2Bx-12=%28x%2B4%29%28x-3%29\"
\n" ); document.write( "20 --> 1+4*20=81 --> \"x%5E2%2Bx-20=%28x%2B5%29%28x-4%29\"
\n" ); document.write( "30 --> 1+4*30=121 --> \"x%5E2%2Bx-30=%28x%2B6%29%28x-5%29\"
\n" ); document.write( "42 --> 1+4*42=169 --> \"x%5E2%2Bx-42=%28x%2B7%29%28x-6%29\"
\n" ); document.write( "Starting to see some paterns, no doubt?...
\n" ); document.write( "So there's an infinite number of k's that'll work. To find the next value in the pattern, square each odd number, subtract one, and divide by 4.
\n" ); document.write( "\"%281%5E2-1%29%2F4=0\"
\n" ); document.write( "\"%283%5E2-1%29%2F4=2\"
\n" ); document.write( "\"%285%5E2-1%29%2F4=6\"
\n" ); document.write( "\"%287%5E2-1%29%2F4=12\"
\n" ); document.write( "\"%289%5E2-1%29%2F4=20\"
\n" ); document.write( "\"%2811%5E2-1%29%2F4=30\"
\n" ); document.write( "\"%2813%5E2-1%29%2F4=42\"
\n" ); document.write( "\"%2815%5E2-1%29%2F4=56\"
\n" ); document.write( "\"%2817%5E2-1%29%2F4=72\"
\n" ); document.write( "Answer your question?
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