To simplify the expression \((3xy - 2xz + yz) + (2xy - 4xz - 5yz)\), we start by removing the parentheses and combining like terms.
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Write out the expression without parentheses: \[ 3xy - 2xz + yz + 2xy - 4xz - 5yz \]
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Now, group the like terms:
- The \(xy\) terms: \(3xy + 2xy\)
- The \(xz\) terms: \(-2xz - 4xz\)
- The \(yz\) terms: \(yz - 5yz\)
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Combine each group:
- For \(xy\): \[ 3xy + 2xy = 5xy \]
- For \(xz\): \[ -2xz - 4xz = -6xz \]
- For \(yz\): \[ yz - 5yz = -4yz \]
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Now, put it all together: \[ 5xy - 6xz - 4yz \]
Thus, the expression equivalent to \((3xy - 2xz + yz) + (2xy - 4xz - 5yz)\) is \[ \boxed{5xy - 6xz - 4yz} \]