\(8x^2y-18y\)

\(=2y\left(x^2-9\right)\)

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

\(3x^3+6x^2+3x-12xy^2\)

\(=3x\left(x^2+2x+1-4y^2\right)\)

\(=3x\left[\left(x+1\right)^2-\left(2y\right)^2\right]\)

\(=3x\left(x+1-2y\right)\left(x+1+2y\right)\)

lẹ

gấp

Mày ra câu hỏi từ từ người ta trả lới cho chứ cứ hối người ta 😡

b) \(3x\left(x-2y\right)+4y\left(2y-x\right)+2\left(3-4y\right)\)

\(=3x\left(x-2y\right)-4y\left(x-2y\right)+2\left(3-4y\right)\)

\(=\left(x-2y\right)\left(3x-4y\right)+2\left(3x-4y\right)\)

\(=\left(3x-4y\right)\left[\left(x-2y\right)+2\right]\)

1. C

2. B

3. D

4. A

5. D

6. B

7. B

8. D

9. A

10. C

tick mk nha

a) x² - 7xy - 18y²

= x² + 2xy - 9xy - 18y²

= x(x + 2y) - 9y(x + 2y) 

= (x - 9y)(x + 2y) 

b) 4x² + 8x - 5

= 4x² - 2x + 10x - 5

= 2x(2x - 1) + 5(2x - 1) 

= (2x + 5)(2x - 1)

c) 4x⁴ - 21x²y² + y⁴

= (4x⁴ + 4x²y² + y⁴) -25x²y²

= (2x² + y²) - (5xy)²

= (2x² + 5xy + y²)(2x² - 5xy + y²) 

= \(2\left(x^2+\frac{5}{2}xy+\frac{y^2}{2}\right)2\left(x^2-\frac{5}{2}xy+\frac{y^2}{2}\right)\)

= \(4\left[\left(x+\frac{5}{4}y\right)^2-\frac{25}{16}y^2+\frac{y^2}{2}\right]\left[\left(x-\frac{5}{4}\right)y^2-\frac{25}{16}y^2+\frac{y^2}{2}\right]\)

\(=4\left(x+\frac{5}{4}y-\frac{\sqrt{17}}{4}y\right)\left(x+\frac{5}{4}y+\frac{\sqrt{17}}{4}y\right)\left(x-\frac{5}{4}y-\frac{\sqrt{17}y}{4}\right)\left(x-\frac{5}{4}y+\frac{\sqrt{17y}}{4}\right)\)

Trả lời:

a, x² - 7xy - 18y² 

= x² - 9xy + 2xy - 18y²

= ( x² - 9xy ) + ( 2xy - 18y² )

= x ( x - 9y ) + 2y ( x - 9y )

= ( x + 2y ) ( x - 9y )

b, 4x² + 8x - 5

= 4x² + 10x - 2x - 5

= ( 4x² + 10x ) - ( 2x + 5 )

= 2x ( 2x + 5 ) - ( 2x + 5 )

= ( 2x - 1 ) ( 2x + 5 )