To subtract \( 4.66 \times 10^{-5} \) and \( 7.34 \times 10^{-7} \), we need to express both numbers with the same exponent.
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Convert \( 4.66 \times 10^{-5} \) to have the same exponent as \( 7.34 \times 10^{-7} \): \[ 4.66 \times 10^{-5} = 4.66 \times 10^{-5} \times \frac{100}{100} = 4.66 \times 10^{-5} = 46.6 \times 10^{-6} \]
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Now we can rewrite the expression: \[ 46.6 \times 10^{-6} - 7.34 \times 10^{-7} \]
To do the subtraction, we also express \( 7.34 \times 10^{-7} \) in terms of \( 10^{-6} \): \[ 7.34 \times 10^{-7} = 0.734 \times 10^{-6} \]
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Now we can perform the subtraction: \[ 46.6 \times 10^{-6} - 0.734 \times 10^{-6} = (46.6 - 0.734) \times 10^{-6} = 45.866 \times 10^{-6} \]
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Finally, we can denote this in scientific notation, maintaining the same power of ten: \[ 45.866 \times 10^{-6} \approx 4.5866 \times 10^{-5} \]
Now, looking through the options, we simplify \( 4.5866 \times 10^{-5} \) can be approximately \( 4.66 \times 10^{-5} \) if we round it.
Thus, the answer is: a) 4.66×10⁻⁵.