整式的乘法...(1)﹙3x+4y﹚﹙x-2y﹚ (2)12x²-﹙3x+y﹚﹙4x-3y﹚ (3)﹙x-y﹚
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(1)﹙3x+4y﹚﹙x-2y﹚

=3x²-6xy+4xy-8y²

=3x²-2xy-8y²;

(2)12x²-﹙3x+y﹚﹙4x-3y﹚

=12x²-12x²+9xy-4xy+3y²

=5xy+3y²;

(3)﹙x-y﹚²

=x²-2xy+y²;

(4)﹙-2x+3﹚²

=4x²-12x+9;

(5)﹙2x-y﹚﹙2x+y﹚-﹙x-3y﹚²

=4x²-y²-x²-9y²+6xy

=3x²+6xy-10y²;

(6)﹙-n﹚的4次方÷﹙-n﹚

=-n³;

(7)y•y+(-y)的7次方÷(-y的4次方)

=y²+y³;

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