Question

Tìm x 

1.(x-1)(x+1)=3

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

3.7x+4(5-x)=3

Answer 1

<=>\(1.x^2-1=3=>x^2=4=\left(+-2\right)^2=>x=+-2\)

Answer 2

Trả lời:

1, \(\left(x-1\right)\left(x+1\right)=3\)

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

\(\Leftrightarrow x^2=4\)

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

Vậy S = { 2 ; - 2 }

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

\(\Leftrightarrow x^3-1-x\left(x^2-4\right)=5\)

\(\Leftrightarrow x^3-1-x^3+4x=5\)

\(\Leftrightarrow4x-1=5\)

\(\Leftrightarrow4x=6\)

\(\Leftrightarrow x=\frac{3}{2}\)

Vậy \(S=\left\{\frac{3}{2}\right\}\)

3, 7x + 4 ( 5 - x ) = 3

<=> 7x + 20 - 4x = 3

<=> 3x + 20 = 3

<=> 3x = - 17

<=> x = - 17/3

Vậy S = { - 17/3 }

Answer 3

1. (x -1)(x + 1) = 3

=> x² - 1= 3

=> x² = 4

=> x ² = 2²

=> x = \(\pm2\) 

2. (x - 1)(x² + x + 1) - (x - 2)(x + 2)x = 5

<=> x³ - 1 - x³ + 4x = 5

<=> 4x = 6

<=> x = 1,5

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

<=> 7x + 20 - 4x = 3

<=> 3x = -17

<=> x = -17/3