Question

1. làm tính nhân

a.-4x^2.(5x-3)

b. (2x^2-x+ 5 ) . (4-3x )

c.(-3y + x ) (2x-y+5)

d. -2/3 xy (6x^2+7xy-5/4)

bai 2 khai triển HĐT :

a. x^2 -1

b. x^2 - 16

c. 4x^2 -9

d. 25/16 - x^2

Answer 1

a) -4x² .( 5x - 3 ) = -20x³ + 12x²

^{b) ( 2x^2 - x +5 ) (4 - 3x ) = 8x^2 - 4x +20 - 6x^3 +3x^2 -15x}

^{= 2x^2 + 3x^2 - 19x +20}

^{c ) ( -3y +x ) ( 2x -y +5) = -6xy + 3y^2 - 15 + 2x^2 - xy +5x}

^{= -7xy + 3y^2 + 2x^2 -15 + 5x}

Answer 2

d) nhân -2/3xy với từng hạng tử = - 4x³y - 14/3 x²y² + 5/6 xy

Bài 2

a) x^2 - 1 = x² - 1² = ( x+y ) ( x-y )

b) x² - 16 = x² - 4² = (x +4) .( x - 4 )

c) 4x² - 9 = ( 2x )² - 3² = (2x +3 ) .( 2x-3 )

d) 25/16 - x² = ( 5/4 )² - x² = ( 5/4 +x ) . ( 5/4 - x )

Answer 3

Bài 2:

a) \(x^2-1\)

\(=\left(x-1\right)\left(x+1\right)\)

b) \(x^2-16\)

\(=x^2-4^2\)

\(=\left(x-4\right)\left(x+4\right)\)

c) \(4x^2-9\)

\(=\left(2x\right)^2-3^2\)

\(=\left(2x-3\right)\left(2x+3\right)\)

d) \(\dfrac{25}{16}-x^2\)

\(=\left(\dfrac{5}{4}\right)^2-x^2\)

\(=\left(\dfrac{5}{4}-x\right)\left(\dfrac{5}{4}+x\right)\)