tolong yakkk....pke cara kerja yg nmr 4 bgian a,b,d

a. 3x( 2x'2 - 5y + 4 ) = ( 3x . 2x'2 ) - ( 3x . 5y ) + ( 3x . 4 ) = 6x'3 - 15xy + 12x

b. ( 3k - 4 )( 1 - 2k ) = ( 3k . 1 ) - ( 3k . 2k ) - ( 4 . 1 ) + ( 4 . 2k ) = 3k - 6k'2 - 4 + 8k = 11k - 6k'2 - 4

c. ( 3 - a )( 3a + 4 )( a - 2 ) = ( 3 - a )( ( 3a . a ) - ( 3a . 2 ) + ( 4 . a ) - ( 4 . 2 ) = ( 3 - a )( 3a'2 - 6a + 4a ) = ( 3 - a )( 3a'2 - 2a ) = (( 3 . 3a'2 ) - ( 3 . 2a ) - ( a . 3a'2 ) + ( a . 2a )) = 9a'2 - 6a - 3a'3 + 2a'2 = 11a'2 - 6a - 3a'3

Kalau gak salah begitu. Terimakasih ^_^