To simplify the expression \((x² + 5x - 7) - (3x² - 4x - 14)\), we'll first distribute the negative sign and then group like terms.
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Distribute the negative sign: \[ (x² + 5x - 7) - (3x² - 4x - 14) = x² + 5x - 7 - 3x² + 4x + 14 \]
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Now, combine like terms:
- For \(x²\) terms: \(x² - 3x² = -2x²\)
- For \(x\) terms: \(5x + 4x = 9x\)
- For constant terms: \(-7 + 14 = 7\)
- Putting it all together, we get: \[ -2x² + 9x + 7 \]
Thus, the final expression in descending powers is: \[ -2x² + 9x + 7 \]