Bài 6 ; tính nhanh:
a, A =\(1993^{1^{2\times3\times4\times......\times1994}}\)
b, B =\(1994^{\left(225-1^2\right)\times\left(225-2^2\right).......\left(225-50^2\right)}\)
c, C =\(\frac{2^{10}\times3^{31}+2^{40}\times3^6}{2^{11}\times3^{31}+2^{41}\times3^6}\)