Упростите выражение \(\frac{x^2-16}{x+7}\cdot \frac{1}{x^2-4x}-\frac{x-4}{x^2-7x}\)

• \(-\frac{6}{x^2-49}\)
• \(\frac{6}{x^2-49}\)
• \(\frac{6x}{x^2-49}\)
• \(-\frac{6x}{x^2-49}\)