八下数学分解因式的题（m+n）²-n² 49（a-b）²-16（a+b）² （2
4个回答

（m+n）²-n²

=(m+n+n)(m+n-n)

=m(m+2n)

49（a-b）²-16（a+b）²

[7(a-b)+4(a+b)][7(a-b)-4(a+b)]

=(11a-3b)(3a-11b)

（2x+y）²-（x+2y）²

=[(2x+y)+(x+2y)][(2x+y)-(x+2y)]

=(3x+3y)(x-y)

=3(x+y)(x-y)

1/3m²-3n²

=1/3(m²-9n²)

=1/3(m+3n)(m-3n)

（a+b）²-（a-b）²

=[(a+b)+(a-b)][(a+b)-(a-b)]

=2a×2b

=4ab

（9a+4b）²-（3a-b）²

=[(9a+4b)+(3a-b)][9a+4b)-(3a-b)]

=(12a+3b)(6a+5b)

=3(4a+b)(6a+5b)

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