Respuesta :

The answer is:  "12.16 * 10²² " .
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Explanation:
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Given:
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  (1.9 * 10³) * (6.4 × 10¹⁸)  ; Multiply to find the answer in "scientific notation" ;
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Note:
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  (1.9 * 10³) * (6.4 × 10¹⁸) ;

= 1.9 * 10³ * 6.4 * 10¹⁸  ;

= 1.9 * 6.4 * 10³ * 10¹⁸  ;
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Note the following property of exponents:
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  xᵃ * xᵇ = x⁽ᵃ⁺ᵇ⁾  ;
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 10³ * 10¹⁸ = 10⁽³⁺¹⁸⁾ = 10²¹ ;
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So; we have:
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  1.9 * 6.4 * 10²¹ ;

= (1.9 * 6.4) * 10²¹ ;

= 12.16 * 10²¹ ; 
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To write a number in scientific notation, there must be a single digit whole number; followed by {a decimal point and any significant figures to the left or right of that number}; multiplied by:  10^(raised to the exponential power of the appropriate positive or negative number).
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So;  we have:
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12.16 * 10²¹ .
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The "12.16" portion becomes:  "1.216" ; and the "10²¹ " becomes "10²² "since an extra decimal place has to be moved to the right).
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 The answer is:  "12.16 * 10²² " .
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