efetue as operações abaixo:
a)4,02•10^2 + 3,07•10^3
b)-12,07•10^3 - 0,49•10^5
c)420•10^-4 - 4,20•10^-6
d)-72,4•10^-3 + 128,5•10^3
E)13,2•10^2 + 44•10^0
F) 0,37•10^4 + 428•10^3
G) -1,49•10^7 + 0,39•10^-2