Explications étape par étape:
a/
[tex] \frac{ {25}^{7} \times { {5}^{3} }^{ - 7} }{ {5}^{4} \times {5}^{ - 9 } } = a[/tex]
[tex]a = \frac{ { {5}^{2} }^{7} \times {5}^{ - 21} }{ {5}^{4 + ( - 9)} } [/tex]
[tex]a = \frac{ {5}^{14} \times {5}^{ - 21} }{ {5}^{ - 5} } [/tex]
[tex]a = \frac{ {5}^{ - 7} }{ {5}^{ - 5} } [/tex]
[tex]a = {5}^{ - 7 - ( - 5)} = {5}^{ - 7 + 5} = {5}^{ - 2} [/tex]
b/
c/
[tex]c = 0.000234 \times {10}^{ - 9} = 2.34 \times {10}^{4} \times {10}^{ - 9} = 2.34 \times {10}^{ - 5} [/tex]
[tex]d = 1789.456 \times {10}^{ - 7} = 1.789456 \times {10}^{ - 3} \times {10}^{ - 7} = 1.789456 \times {10}^{ - 10} [/tex]
