c1 . x3 - 7x - 6
= x3 - 7x + 8 - 14
= ( x + 2)( x2 - 2x + 4) - 7( x + 2)
= ( x + 2)( x2 - 2x - 3)
= ( x + 2)( x2 + x - 3x - 3)
= ( x + 2)[ x( x + 1) - 3( x + 1 ) ]
= ( x + 1)( x + 2 )( x - 3)
c2. x3 - 7x - 6
= x3 - x - 6x - 6
= x( x2 - 1) - 6( x + 1)
= x( x + 1)(x - 1) - 6( x + 1)
= ( x + 1)( x2 - x - 6)
= ( x + 1)( x2 + 2x - 3x - 6)
= ( x + 1)[ x( x + 2) - 3( x + 2) ]
= ( x + 1)(x + 2)( x - 3)
c3 . x3 - 7x - 6
= x3 + x2 - x2 - 7x - 6
= x2( x + 1) - ( x2 + 7x + 6)
= x2( x + 1) - ( x2 + x + 6x + 6)
= x2( x + 1) - [ x( x + 1) + 6( x + 1) ]
= x2( x + 1) - ( x + 1)( x + 6)
= ( x + 1)( x2 - x - 6)
= ( x + 1)( x2 + 2x - 3x - 6)
= ( x + 1)[ x( x + 2) - 3( x + 2) ]
= ( x + 1)( x + 2)( x - 3)
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