d, $ x ^ 3 $ - 19x - 30
= $ x ^ 3 $ - $ 5x ^ 2 $ + $ 5x ^ 2 $ - 25x + 6x - 30
= $ x ^ 2 $ ( x - 5 ) + 5x ( x - 5 ) + 6 ( x - 5 )
= ( $ x ^ 2 $ + 5x + 6 )( x - 5 )
= ( $ x ^ 2 $ + 2x + 3x + 6 )( x - 5 )
= [ x ( x + 2 ) + 3 ( x + 2 ) ] ( x - 5 )
= ( x + 3 )( x + 2 )( x - 5 )
e, $ x ^ 3 $ - 7x - 6
= $ x ^ 3 $ - $ 3x ^ 2 $ + $ 3x ^ 2 $ - 9x + 2x -6
= $ x ^ 2 $ ( x - 3 ) + 3x ( x - 3 ) + 2 ( x - 3 )
= ( $ x ^ 2 $ + 3x + 2 )( x - 3 )
= ( $ x ^ 2 $ + x + 2x + 2 )( x - 3 )
= [ x ( x + 1 ) + 2 ( x + 1 ) ]( x - 3 )
= ( x + 2 )( x + 1 )( x - 3 )
f, $ x ^ 3 $ - $ 5x ^ 2 $ - 14x
= $ x ^ 3 $ - $ 7x ^ 2 $ + $ 2x ^ 2 $- 14x
= $ x ^ 2 $ ( x - 7 ) + 2x ( x - 7 )
= ( $ x ^ 2 $ + 2x )( x - 7 )
= x ( x + 2 )( x - 7 )
#Blackroses
` Chúc ` ` bạn ` ` học ` ` tốt `
