Le principe est : a^n veut dire a puissance n
a^n * a^m = a^(n+m)
1/a^n = a^-n
a^n / a^m = a^(n-m)
a^0 = 1
a^1 = a
a^-1 = 1/a
donc
A=5^8/(5^11*5^7) = 5^8/5^(11+7) = 5^8/5^18 = 5^(8-18) = 5^-10
B = (3,4^-3*3,4^-5) / 3,4^-8 = 3,4^(-3-5) / 3,4^-8 = 3,4^(-8) / 3,4^-8 = 3,4^(-8+8)
B = 3,4^0 = 1
C = (3^4*3^2) / (3^-4*3^7) = 3^(4+2) / 3^(-4+7) = 3^6 / 3^3 = 3^(6-3) = 3^3
D = (2^-3*2^4*2^-2)/(2^5*2^8) = 2^(-3+4-2)/2^(5+8) = 2^-1/2^13 = 2^(-1-13) = 2^-14
