Question

1/ Thực hiện phép nhân : 

a) x² ( 5x³ - x - \(\dfrac{1}{2}\))

b) ( 3xy - x² + y ) \(\dfrac{2}{3}\)x²y

c) x² ( 4x^{3 -} 5xy + 2x ) ( -\(\dfrac{1}{2}\) xy )

2/ Tìm x, biết

a) 3x( 12x - 4 ) - 9x (4x - 3 ) = 30

b ) x( 5 - 2x ) + 2x ( x - 1 )= 15

 

Answer 1

2.

a. 3x(12x - 4) - 9x(4x - 3) = 30

<=> 36x² - 12x - 36x² + 27x = 30

<=> 36x² - 36x² - 12x + 27x = 30

<=> 15x = 30

<=> x = 2

b. x(5 - 2x) + 2x(x - 1) = 15

<=> 5x - 2x² + 2x² - 2x = 15

<=> -2x² + 2x² + 5x - 2x = 15

<=> 3x = 15

<=> x = 5

Answer 2

a) x² ( 5x³ - x - 2323x²y=  6969x³y²- 2323x⁴y+ 2323x²y²

c) x² ( 4x^{3 -} 5xy + 2x ) ( -