document.write( "Question 165834: Factor completely:
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document.write( "3x2 + 2x – 8\r
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Algebra.Com's Answer #122231 by Alan3354(69443)![]() ![]() You can put this solution on YOUR website! Factor completely: \n" ); document.write( "3x2 + 2x – 8 \n" ); document.write( "---------------- \n" ); document.write( "The factors will be (ax + b)*(cx + d) \n" ); document.write( "The trick is to find a, b, c and d \n" ); document.write( "These problems in class almost always use integers, so let's assume they are. \n" ); document.write( "If they're not, it's an impossible problem. \n" ); document.write( "--------- \n" ); document.write( "The product a*c = 3, and the product b*d = -8. Since it's negative, we know that either b or d is negative, but not both of them. \n" ); document.write( "Since a*c = 3, one of them is 1 and the other is 3. \n" ); document.write( "b and d can be 1 & 8 or 2 and 4. \n" ); document.write( "We also know that ad + bc = 2 \n" ); document.write( "We can try some numbers. \n" ); document.write( "(x + 2)*(3x - 4) = 3x^2 + 2x - 8 Sometimes you get lucky. There are 4 possibilities, the 1st one was the answer. \n" ); document.write( "----------------- \n" ); document.write( "(x + 2)*(3x - 4) = 3x^2 + 2x - 8 \r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |