Bonsoir
1.5 x 10^-10 x 0.54 x 10^-1 sur 12 x(10^8)²
= 0.81 x 10^-11 sur 12 x 10^16
= 0.0675 x 10^-27
= 6.75 x 10² x 10^-27 = 6.75 x 10^-25
7 x 10² x 90.1 x 10^-3
= 630.7 x 10^-1
= 6.307 x 10^-3 x 10^-1
= 6.307 x 10^-4
(-4)^7 x (-4)²
= (-4)^9 = - 262 144
5^-1 x 5 x 5^-11 sur (5^-2)^4
= 5^-11 sur 5^-8
= 5^-3