Question

Tìm x biết

A. 2.(3x-1)-5(x-3)-9(2x-4)=24

B. 2x²   +4( x² -1)=2x (3x+ 1)

C. 2x (5-3x)+2x (3x-5)-3(x-7)=4

Đ. 5x(x+1)-4x(x+2=1-x

Answer 1

k mk đi

ai k mk 

mk k lại

thanks

Answer 2

không ai trả lời 

a,\(2\left(3x-1\right)-5\left(x-3\right)-9\left(2x-4\right)=24\)

\(< =>6x-2-5x+15-18x+36=24\)

\(< =>-29x+49=24< =>29x=25< =>x=\frac{25}{29}\)

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

\(< =>2x^2+4x^2-4=6x^2+2x\)

\(< =>2x=-4< =>x=-\frac{4}{2}=-2\)

c, \(2x\left(5-3x\right)+2x\left(3x-5\right)-3\left(x-7\right)=4\)

\(< =>10x-6x^2+6x^2-10x-3x+21=4\)

\(< =>-3x=4-21=-17< =>x=\frac{17}{3}\)

d, \(5x\left(x+1\right)-4x\left(x+2\right)=1-x\)

\(< =>5x^2+5x-4x^2-8x=1-x\)

\(< =>x^2-3x+x-1=0\)

\(< =>x^2-2x-1=0\)

\(< =>\left(x-1\right)^2=2\)

\(< =>\orbr{\begin{cases}x-1=\sqrt{2}\\x-1=-\sqrt{2}\end{cases}}\)

\(< =>\orbr{\begin{cases}x=1+\sqrt{2}\\x=1-\sqrt{2}\end{cases}}\)

Answer 3

Sai rồi bn:)

a, \(2\left(3x-1\right)-5\left(x-3\right)-9\left(2x-4\right)=24\)

\(\Leftrightarrow6x-2-5x+15-18x+36=24\)

\(\Leftrightarrow-17x+25=0\Leftrightarrow x=\frac{25}{17}\)

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

\(\Leftrightarrow2x^2+4x^2-4=6x^2+2x\)

\(\Leftrightarrow-4-2x=0\Leftrightarrow x=-2\)

c, \(2x\left(5-3x\right)+2x\left(3x-5\right)-3\left(x-7\right)=4\)

\(\Leftrightarrow10x-6x^2+6x^2-10x-3x+21=4\)

\(\Leftrightarrow-3x+17=0\Leftrightarrow x=\frac{17}{3}\)

d, \(5x\left(x+1\right)-4x\left(x+2\right)=1-x\)

\(\Leftrightarrow5x^2+5x-4x^2-8x=1-x\)

\(\Leftrightarrow x^2-3x-1+x=0\Leftrightarrow x^2-2x-1=0\)

\(\Leftrightarrow x^2-2x+1-2=0\Leftrightarrow\left(x-1\right)^2=2\)

\(\Leftrightarrow\orbr{\begin{cases}x-1=\sqrt{2}\\x-1=-\sqrt{2}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\sqrt{2}+1\\x=-\sqrt{2}+1\end{cases}}}\)

Answer 4

A) 2( 3x - 1 ) - 5( x - 3 ) - 9( 2x - 4 ) = 24

<=> 6x - 2 - 5x + 15 - 18x + 36 = 24

<=> -17x + 49 = 24

<=> -17x = -25

<=> x = 25/17

B) 2x² + 4( x² - 1 ) = 2x( 3x + 1 )

<=> 2x² + 4x² - 4 - 6x² - 2x = 0

<=> -4 - 2x = 0

<=> 2x = -4

<=> x = -2

C) 2x( 5 - 3x ) + 2x( 3x - 5 ) - 3( x - 7 ) = 4

<=> 2x( 5 - 3x + 3x - 5 ) - 3x + 21 = 4

<=> 10x - 6x² + 6x² - 10x - 3x + 21 = 4

<=> -3x + 21 = 4

<=> -3x = -17

<=> x = 17/3

D) 5x( x + 1 ) - 4x( x + 2 ) = 1 - x

<=> 5x² + 5x - 4x² - 8x - 1 + x = 0

<=> x² - 2x - 1 = 0

<=> x² - 2x + 1 - 2 = 0

<=> ( x - 1 )² = 2

<=> \(\orbr{\begin{cases}x-1=\sqrt{2}\\x-1=-\sqrt{2}\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=1+\sqrt{2}\\x=1-\sqrt{2}\end{cases}}\)