( x + y + z )” - ( x - y - z )”
= [ (x+y+z) + (x-y-z) ][ (x+y+z) - (x-y-z) ]
= ( x +y +z +x -y -z )( x +y +z -x +y +z )
= ( 2x )( 2y + 2z )
= 4x( y + z )
(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)
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