4. Упростите выражение: $$\frac{5}{x-7}-\frac{2}{x}+\frac{3x+28}{49-x^2}$$

$$\frac{5}{x-7}-\frac{2}{x}+\frac{3x+28}{49-x^2} = \frac{5}{x-7}-\frac{2}{x}-\frac{3x+28}{x^2-49} = \frac{5}{x-7}-\frac{2}{x}-\frac{3x+28}{(x-7)(x+7)} = $$ $$ = \frac{5x(x+7)-2(x-7)(x+7)-(3x+28)x}{x(x-7)(x+7)} = \frac{5x^2+35x-2(x^2-49)-(3x^2+28x)}{x(x-7)(x+7)} = $$ $$ = \frac{5x^2+35x-2x^2+98-3x^2-28x}{x(x-7)(x+7)} = \frac{7x+98}{x(x-7)(x+7)} = \frac{7(x+14)}{x(x-7)(x+7)}$$