Question

[Hân Hân]

P/s : Ai làm được mấy bài ở đây thì giúp mình nhé. Chứ mình bất lực lắm rồi :((

Bài 1 Rút gọn 

1 ) 2x . ( x - 5 ) + ( x - 2 ) . ( x + 3 )

2) ( 2x -  ) . ( 1 - x ) - ( x - 3 ) . ( -2 x )

3) ( 4x - 3 ) . ( 4x - 3 ) - ( 3x + 2 ) . ( 3x - 2 )

4) ( 2x - 1 ) . ( 2x + 1 ) - 4 . ( x² + 1 )

5) 3x ( 2x - 8 ) - ( 2 - 6x ) . ( 5 + x )

6 ) x . ( 3x - 18 ) . ( x - 4 ) . ( x - 2 ) + 8

Bài 2 Tìm x

1 ) 3 x . ( x - 2 ) - 3 x² = 1

2 ) x . ( 6x - 5 ) - 3x . ( 2x - 3 ) = 7

3 ) x . ( 2x - 1 ) + 2 . ( 1 - x² ) = 0

4 ) 5 . ( x² -1 ) + x . ( 1 - 5 x ) = x - 2 

5 ) 3x . ( 4x - 1 ) - ( 2x + 1 ) . ( 5 + 6x ) = 0

6 ) ( x + 3 ) . ( 2x - 1 ) - ( x - 4 ) . ( 2x + 1 ) = 10

7 ) ( 3x + 4 ) . ( 2x - 1 ) + 6x . ( 1 - x ) = 0

8 ) 2x . (  x² - 1 ) + x . ( 1 - 3x - 2x² ) = -x - 27 

Answer 1

[Nguyễn Lê Phước Thịnh]

7: Ta có: \(\left(3x+4\right)\left(2x-1\right)+6x\left(1-x\right)=0\)

\(\Leftrightarrow6x^2-3x+8x-4+6x-6x^2=0\)

\(\Leftrightarrow11x=4\)

hay \(x=\dfrac{4}{11}\)

8: Ta có: \(2x\left(x^2-1\right)+x\left(-2x^2-3x+1\right)=-x-27\)

\(\Leftrightarrow2x^3-2x-2x^3-3x^2+x+x+27=0\)

\(\Leftrightarrow x^2=9\)

hay \(x\in\left\{3;-3\right\}\)