\(a,3.\left(12x-4\right)-9.\left(4x-3\right)=30\)
=>\(36x-12-36x-27=30\)
=>\(\left(36x-36x\right)-\left(12+27\right)=30\)
=> \(0-39=30\) ( sai )
=> \(x\in\varnothing\)
\(b,x\left(5-2x\right)+2.\left(x-1\right)=15\)
=>\(5x-2x^2+2x-2=15\)
=>\(7x-2x^2-2=15\)
=>\(7x-2x^2=15+2=17\)
( đến đoạn này thì chịu , HS 6-7 làm bài )
a) 3x( 12x - 4 ) - 9x( 4x - 3 ) = 30
=> 3x. 12x - 3x. 4x - 9x. 4x - 9x. 3 = 30
=> 36x2 - 12x - 36x2 + 27x = 30
=> 27x - 12x = 15x
=> 15x = 30
Vậy x = 2
b) x( 5 - 2x ) + 2x( x - 1 ) = 15
=> x. 5 - x. 2x + 2x. x - 2x. 1 = 15
=> 5x - 2x2 + 2x2 - 2x = 15
=> 5x - 2x = 3x
=> 3x = 15
Vậy x = 3
a) 3x( 12x - 4 ) - 9x( 4x - 3 ) = 30
=> 3x. 12x - 3x. 4x - 9x. 4x - 9x. 3 = 30
=> 36x2 - 12x - 36x2 + 27x = 30
=> 27x - 12x = 15x
=> 15x = 30
Vậy x = 2
b) x( 5 - 2x ) + 2x( x - 1 ) = 15
=> x. 5 - x. 2x + 2x. x - 2x. 1 = 15
=> 5x - 2x2 + 2x2 - 2x = 15
=> 5x - 2x = 3x
=> 3x = 15
Vậy x = 3
