Bonjour !
a)
[tex] {10}^{ - 9} \times {10}^{12} = {10}^{ - 9 + 12} = {10}^{3} [/tex]
b)
[tex] \frac{ {10}^{ - 7} }{ {10}^{8} } = {10}^{ - 7- 8} = {10}^{ - 15} [/tex]
c)
[tex]( {10}^{ - 3})^{6} = {10}^{- 3 \times 6} = {10}^{ - 18} [/tex]
d)
[tex] \frac{ {10}^{10} }{ {10}^{ - 5} } = {10}^{10 - ( -5 )} = {10}^{15} [/tex]
e)
[tex] \frac{ {10}^{21} }{ {10}^{ - 4} \times {10}^{ - 18} } = \frac{10 ^{21} }{ {10}^{ - 22} } = {10}^{21 + 22} = {10}^{44} [/tex]
Bonne soirée
