Упростите выражение 5/(x-7)-2/x-3x/(x^2-49)+21/(49-x^2).

\[\frac{5^{\backslash x(x + 7)}}{x - 7} - \frac{2^{\backslash x^{2} - 49}}{x} - \frac{3x^{\backslash x}}{x^{2} - 49} + \frac{21^{\backslash\text{-}x}}{49 - x^{2}} =\]

\[= \frac{5x^{2} + 35x - 2x^{2} + 98 - 3x^{2} - 21x}{x\left( x^{2} - 49 \right)} =\]

\[= \frac{14x + 98}{x\left( x^{2} - 49 \right)} = \frac{14(x + 7)}{x(x - 7)(x + 7)} =\]

\[= \frac{14}{x^{2} - 7x}.\]