Ответы и объяснения

2013-09-29T22:02:25+04:00
а) (х-9)/ (х^2 - 9)  + 3 / x(x-3) = (x^2 -9x +3x +9 ) / x(x^2-9) = (x^2 - 6x + 9) / x(x^2-9) = (x-3)^2 / x (x+3)(x-3) = (x-3)/( x^2+3x)
б) 1/(x-2) - 6x / (x-2)(x^2+2x+4) = (x^2+2x+4-6x) / (x^3 - 8) = (x^2-4x+4) / (x^3 - 8) =
(x-2)^2 / (x-2)(x^2+2x+4) = (x-2) / (x^2 +2x + 4 )
в) 3/x + 21/ x(x-7) - (4-x)/(x-7) = (3x - 21 +21 -4x +x^2) / x(x-7) = (x^2 -x) / x(x-7) = x(x-1)/x(x-7) = (x-1) / (x-7)