Question

Tim nghiem :

a) A ( x ) = ( 6x + 3 ) - ( 2x + 1 )

b) B ( x ) = ( \(^{x^2}\) - 5x + 5 ) - ( 5x + 5 )

c) C ( x ) = \(^{x^2}\) - 8x

d) D ( x ) = \(x^2\) - 5x + 4

giup minh voi mai ninh nop roi.

Answer 1

a) A(x) = 0

=> 6x + 3 - (2x + 1)

=> 6x + 3 - 2x - 1 = 0

=> (6x - 2x) + (3 - 1) = 0

=> 4x + 2 = 0

=> 4x = -2

=> x = -2 : 4

=> x = -0,5

Vậy ...

b) B(x) = 0

=> (x² + 5x - 5) - (5x - 5) = 0

=> x² + 5x - 5 - 5x + 5 = 0

=> x² + 5x - 5x = 0

=> x² = 0

=> x = 0

Vậy ...

c) C(x) = x² - 8x

=> x² - 8x = 0

=> x² = 8x

=> x = 8 ( Chia mỗi bên cho x)

Vậy ...

d) D(x) = x² - 5x + 4

=> x² - x - 4x + 4 = 0

=> x.(x - 1) - 4.(x - 1) = 0

=> (x - 4).(x - 1) = 0

=> \(\left[{}\begin{matrix}x-4=0\\x-1=0\end{matrix}\right.\) => \(\left[{}\begin{matrix}x=4\\x=1\end{matrix}\right.\)

Vậy x = 4; x = 1 là nghiệm của D(x)