document.write( "Question 126457: (x+1)(x+2)(x+3)(x+4) = 120 \n" ); document.write( "
Algebra.Com's Answer #92643 by bucky(2189)![]() ![]() ![]() You can put this solution on YOUR website! An analytical way of doing this problem is to look at the factors of 120. \n" ); document.write( ". \n" ); document.write( "Divide it by 2 and you get 60*2 \n" ); document.write( ". \n" ); document.write( "Divide the 60 by 4 to get 4 and 15 as factors of 60 and you have that the factors of 120 \n" ); document.write( "have become 4*15*2. \n" ); document.write( ". \n" ); document.write( "Then factor 15 into 5*3 and substitute that result for 15 to get that the factors of 120 \n" ); document.write( "are 4*3*5*2. If you multiply these factors together you do get 120, so our factors check out \n" ); document.write( "to be OK. \n" ); document.write( ". \n" ); document.write( "Now arrange the factors in ascending order: 2*3*4*5 \n" ); document.write( ". \n" ); document.write( "Notice significantly that each of these factors increases by 1. Now compare them to the \n" ); document.write( "factors on the left side of the problem you were given ... \n" ); document.write( ". \n" ); document.write( "(x+1)*(x+2)*(x+3)*(x+4) \n" ); document.write( ". \n" ); document.write( "Each of those factors is 1 greater than the preceding factor ... and there are four of them \n" ); document.write( "just as we found in the four factors 2*3*4*5 \n" ); document.write( ". \n" ); document.write( "What do we get if we set the first factor x + 1 equal to 2 ... we find x = 1 \n" ); document.write( ". \n" ); document.write( "What do we get if we set the second factor x + 2 equal to 3 ... we again find x = 1 \n" ); document.write( ". \n" ); document.write( "What do we get if we set the third factor x + 3 equal to 4 ... we again find x = 1 \n" ); document.write( ". \n" ); document.write( "And, finally, what do we get if we set the fourth factor x + 4 equal to 5 ... we again find x = 1 \n" ); document.write( ". \n" ); document.write( "What an interesting outcome. If in each of the four factors: \n" ); document.write( ". \n" ); document.write( "(x+1)*(x+2)*(x+3)*(x+4) \n" ); document.write( ". \n" ); document.write( "we set x = 1, the factors become 2*3*4*5 and this product is 120. So the solution \n" ); document.write( "to this problem is x = 1 \n" ); document.write( ". \n" ); document.write( "Sure was a lot easier to do it this way than to try multiplying out the 4 original factors \n" ); document.write( "and then setting that product equal to 120 and trying to solve that fourth order equation. \n" ); document.write( ". \n" ); document.write( "Hope this is clear enough so that you can follow it through and see what was done to solve \n" ); document.write( "the problem. \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( " |