To solve the equation \( 3x^{3/2} + 25 = 400 \), first, we can isolate the term with \( x \):
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Subtract 25 from both sides: \[ 3x^{3/2} = 400 - 25 \] \[ 3x^{3/2} = 375 \]
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Divide both sides by 3: \[ x^{3/2} = \frac{375}{3} \] \[ x^{3/2} = 125 \]
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To solve for \( x \), raise both sides to the power of \( \frac{2}{3} \): \[ x = 125^{2/3} \]
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We can calculate \( 125^{2/3} \):
- Since \( 125 = 5^3 \), we have: \[ 125^{2/3} = (5^3)^{2/3} = 5^{3 \cdot \frac{2}{3}} = 5^2 = 25 \]
Thus, the solution to the equation \( 3x^{3/2} + 25 = 400 \) is \( x = 25 \).
Therefore, the correct response is: 25