a: ĐKXĐ: \(x\le0\)

b: ĐKXĐ: \(x\le2\)

\(a,ĐK:-3x\ge0\Leftrightarrow x\le0\left(-3< 0\right)\\ b,ĐK:4-2x\ge0\Leftrightarrow-2x\ge-4\Leftrightarrow x\le2\\ c,ĐK:\dfrac{1}{2x-5}\ge0\Leftrightarrow2x-5>0\left(1>0;2x-5\ne0\right)\\ \Leftrightarrow x>\dfrac{5}{2}\\ d,ĐK:\dfrac{4x+7}{-3}\ge0\Leftrightarrow4x+7\le0\left(-3< 0\right)\Leftrightarrow x\le-\dfrac{7}{4}\)

\(\dfrac{2}{2x+1}-1\ge0\Leftrightarrow\dfrac{2}{2x+1}-\dfrac{2x+1}{2x+1}\ge0\)

\(\Leftrightarrow\dfrac{2-\left(2x+1\right)}{2x+1}\ge0\)

\(\Leftrightarrow\dfrac{1-2x}{2x+1}\ge0\)

\(\Rightarrow-\dfrac{1}{2}< x\le\dfrac{1}{2}\)

Câu 3:

a: \(25x-30x^2=5x\left(5-6x\right)\)

b: \(8x\left(x+4y\right)+16\left(x+4y\right)=8\left(x+4y\right)\left(x+2\right)\)

c: \(24x^8y^7-15x^6y^5+18x^6y^3\)

\(=3x^6y^3\left(8x^2y^4-5y^2+6\right)\)

câu 1:

a) 4x( 5x + 9 )

 = 4x5x + 4x9

 = 20x²+36x

b) (3x - 2) ( x+7 )

 = 3xx + 3x7 - 2x - 2 . 7

 = 3x²+ 21x - 2x - 14

 = 3x² +19x - 14

c) (2x- 5 )(x²-7x + 4 )

 = 2xx² - 2x7x + 2x4 - 5x² +5 . 7x - 5.4

 = 2x³- 14x²+8x - 5x ²+ 35x - 20

 = 2x³+ ( - 14x²- 5x² )+(8x+35x) - 20

 = 2x³ - 9x² + 43x - 20

Câu 2 :

a) (5x - 3x)²

  = (5x)² - 2.5x3y + (3y)²

  = 25x² - 30xy +9y

b) (2x - 5)(2x + 5)

 = (2x)² - 5²

  = 4x² - 25

c) (3x - 7y)³

 = ( 3x)³ - 3(3x)²7y + 3.3x(7y)² - (7y)²

 = 27x³ - 189x²y + 441xy²- 343y³

d) (x+5)(x²-5x+25)

 = (x+5)(x²-5x+5²)

 = x³+5³

 = x³+125

Câu 3 : 

a) 25x-30x²

 = 5.5x-5.6xx

 = 5x(5-6x)

b) 8x(x+4y)+16(x+4y)

 = (x+4y)(8x+16)

c) 24x⁸y⁷ -15x⁶y⁵+18x⁶y³

 = 3.8x⁶x²y³y⁴-3.5x⁶y³y²+3.6x⁶y³

 = 3x⁶y³(8x²y⁴-5y²+6)

Câu 3: 

a: \(25x-30x^2=5x\left(5-6x\right)\)

b: \(8x\left(x+4y\right)+16\left(x+4y\right)=8\left(x+4y\right)\left(x+2\right)\)

\(8,=\left(2x-3\right)\left(2x+3\right)\\ 9,=\left(1-5a^2\right)\left(1+5a^2\right)\)

8) \(-9+4x^2=\left(2x\right)^2-3^2=\left(2x-3\right)\left(2x+3\right)\)

9) \(1-25a^4=1-\left(5a^2\right)^2=\left(1-5a^2\right)\left(1+5a^2\right)\)

\(\left(-2022\right)+\left(-250\right)+\left(275+2022\right)\)

\(=\left(-2022\right)-250+275+2022\)

\(=\left[\left(-2022\right)+2022\right]+\left(275-250\right)\)

\(=0+25=25\)

=- 2022 -250+ 275 + 2022

=-2272+2297

=25

_{$\left(-2022\right)+\left(-250\right)+\left(275+2022\right)$}

_{=\left(-2022\right)-250+275+2022$=\left(-2022\right)-250+275+2022$}

_{=\left[\left(-2022\right)+2022\right]+\left(275-250\right)$=\left[\left(-2022\right)+2022\right]+\left(275-250\right)$}

_{=0+25=25$=0+25=25$}

57

57

57

giả sử số đó là 19

19-10=9đáp số 19

x-10=1 số nào đó

10+1=11

Đ/S:11

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

=>-x=4

hay x=-4