3(y-z)的2次方-(2y-z)(-z+2y)

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3(y-z)的2次方-(2y-z)(-z+2y)3(y-z)的2次方-(2y-z)(-z+2y)3(y-z)的2次方-(2y-z)(-z+2y)3(y-z)^2-(2y+z)(-z+2y)=3(y-z

3(y-z)的2次方-(2y-z)(-z+2y)
3(y-z)的2次方-(2y-z)(-z+2y)

3(y-z)的2次方-(2y-z)(-z+2y)
3(y-z)^2-(2y+z)(-z+2y)
=3(y-z)^2-(2y+z)(2y-z)
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=3(y-z)^2-[(2y)^2-z^2]
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=3(y^2-2yz+z^2)-4y^2+z^2
=-y^2-6yz+4z^2

原式=3(y^2-2yz+z^2)-2(-2yz+4y^2+z^2-2yz)
=3y^2-6yz+3z^2+4yz-8y^2-2z^2+4yz
=(3-8)y^2-(6-4-4)yz+(3-2)z^2
=-5y^2+2yz+z^2