حاصل عبارت $(۱ \times \frac{۱}{۷}) - (۲ \times \frac{۱}{۱۴}) + (۳ \times \frac{۱}{۲۱}) - ... + (۲۵ \times \frac{۱}{۱۷۵})$ کدام است؟
$(1 \times \frac{1}{7}) - (2 \times \frac{1}{14}) + (3 \times \frac{1}{21}) - ... + (25 \times \frac{1}{175})=(1 \times \frac{1}{7}) - (2 \times \frac{1}{14}) + (3 \times \frac{1}{21}) -... (23 \times \frac{1}{161})- (24 \times \frac{1}{168})+ (25 \times \frac{1}{175})= (25 \times \frac{1}{175})=\frac{1}{7}$