tính nhanh bằng cách rút gọn \(\frac{21x45}{9x7x5x3}\)\(\frac{36x22x51}{11x17x72}\)\(\frac{1313}{2121}\)x\(\frac{165165}{143143}\)x \(\frac{199319931993}{199519951995}\)
2 Tính nhanh
\(\frac{6x4x18x25}{8x1012x15}\) b) \(\frac{1995}{1996}\)x\(\frac{19961996}{19931993}\)x \(\frac{199319931993}{199519951995}\)