因式分解,9(x-y)²-y²,9a²-4(b＋c)²,（x＋y＋z)²-(x-y-z)²,

因式分解,9(x-y)²-y²,9a²-4(b＋c)²,（x＋y＋z)²-(x-y-z)²,
因式分解,9(x-y)²-y²,9a²-4(b＋c)²,（x＋y＋z)²-(x-y-z)²,

因式分解,9(x-y)²-y²,9a²-4(b＋c)²,（x＋y＋z)²-(x-y-z)²,
9(x-y)²-y²,
=[3(x-y)]²-y²
=[3(x-y)+y][3(x-y)-y]
=(3x-2y)(3x-4y)
9a²-4(b＋c)²,
=(3a)²-[2(b+c)]²
=[3a+2(b+c)][3a-2(b+c)]
=(3a+2b+2c)(3a-2b-2c)
（x＋y＋z)²-(x-y-z)²
=[(x+y+z)+(x-y-z)][(x+y+z)-(x-y-z)]
=2x(2y+2z)
=4x(y+z)

9(x-y)²-y²=(3x-3y+y)(3x-3y-y)=(3x-2y)(3x-4y)
9a²-4(b＋c)²=(3a-2b-2c)(3a+2b+2c)
（x＋y＋z)²-(x-y-z)²=4x(y+z)

根据平方差公式，a^2-b^2=（a-b)*(a+b)

这就是利用平方差分解，
完全平方就是 a" 或 b"，
9( x - y )" - y"
= [ 3( x - y ) + y ][ 3( x - y ) - y ]
= ( 3x - 3y + y )( 3x - 3y - y )
= ( 3x - 2y )( 3x - 4y )
9a" - 4( b + c )"
= [ 3a + 4( ...

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这就是利用平方差分解，
完全平方就是 a" 或 b"，
9( x - y )" - y"
= [ 3( x - y ) + y ][ 3( x - y ) - y ]
= ( 3x - 3y + y )( 3x - 3y - y )
= ( 3x - 2y )( 3x - 4y )
9a" - 4( b + c )"
= [ 3a + 4( b + c ) ][ 3a - 4( b + c ) ]
= ( 3a + 4b + 4c )( 3a - 4b - 4c )
( x + y + z )" - ( x - y - z )"
= ( x + y + z + x - y - z )( x + y + z - x + y + z )
= 2x( 2y + 2z )
= 4x( y + z )

收起

9(x-y)²-y²
=[3(x-y)]²-y²
=[3(x-y)+y]×[3(x-y)-y]
=(3x-2y)(3x-4y)
9a²-4(b+...

全部展开

9(x-y)²-y²
=[3(x-y)]²-y²
=[3(x-y)+y]×[3(x-y)-y]
=(3x-2y)(3x-4y)
9a²-4(b+c)²
=(3a)²-[2(b+c)]²
=[3a-2(b+c)]×[3a+2(b+c)]
=(3a-2b-2c)(3a+2b+2c)
(x+y+z)²-(x-y-z)²
=[x+(y+z)]²-[x-(y+z)]²
=2(y+z)·2x

收起