因式分解(3x+y)的2次方-(x-3y)的2次方,

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因式分解(3x+y)的2次方-(x-3y)的2次方,
因式分解(3x+y)的2次方-(x-3y)的2次方,

因式分解(3x+y)的2次方-(x-3y)的2次方,
(3x+y)²-(x-3y)²
=[(3x+y)+(x-3y)]·[(3x+y)-(x-3y)]
=(4x-2y)(2x+4y)
=4(2x-y)(x+2y)

解;(3x+y)²-(x-3y)²
=[(3x+y)+(x-3y)][(3x+y)-(x-3y)]
=(3x+y+x-3y)(3x+y-x+3y)
=(4x-2y)(2x+4y)
=4(2x-y)(x+2y)

用完全平方公式,把(3x+y)和(x-3y)当成整体
(3x+y)²-(x-3y)²
=[(3x+y)+(x-3y)][(3x+y)-(x-3y)]
=(3x+y+x-3y)(3x+y-x+3y)
=(4x-2y)(2x+4y)
=4(2x-y)(x+2y)