Answers

2014-07-10T21:55:47+08:00
1/x + 1/1+x =  7/12      ^  LCM of    x, (1 + x), & 12 =  12x(1+ x)
to get rid of the denominator multiply the whole expression by the LCM
Thus
12x(1+x)[1/x + 1/1+x]    =  12x(1+x)7/12  =  7x(1 + x)
  12(1+x) + 12x   =    7x + 7x²
   12 + 12x + 12x = 7x +7x²
     12 +17x = 7x²
                      0 = 7x² -17x -12
                     (7x +4)(x - 3) = 0
                     x   =    -4/7    0r    x = 3

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