Question

Tìm x : 

a) 3x( x - 10 ) = x - 10

b) x( x + 7 ) - ( 4x + 28 ) = 0

c) x( x - 4 ) = 2x - 8

d) ( 2x + 3 )( x - 1 ) + ( 2x - 3 )( x - 1 ) = 0

Answer 1

3x(x - 10) = x - 10

(x - 10)(3x - 1) = 0

Th1:

x - 10 = 0

x = 10

TH2:

3x - 1 = 0

3x = 1

x = 1/3

Vậy x = 10 hoặc x = 1/3

x(x + 7) - (4x + 28) = 0

x(x + 7) - 4(x + 7) = 0

(x + 7)(x - 4) = 0

Th1:

x + 7 = 0

x = - 7

Th2:

x - 4 = 0

x = 4

Vậy x = - 7 hoặc x = 4

x(x - 4) = 2x - 8

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

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

Th1:

x - 2 = 0

x = 2

Th2:

x - 4 = 0

x = 4 

Vậy x = 2 hoặc x = 4

(2x + 3)(x - 1) + (2x - 3)(x - 1) = 0

(x - 1)(2x + 3 + 2x - 3) = 0

4x(x - 1) = 0

Th1:

x = 0

Th2:

x - 1 = 0

x = 1

Vậy x = 0 hoặc x = 1

Answer 2

a)

\(3x\left(x-10\right)=x-10\)

\(\Rightarrow3x\left(x-10\right)-\left(x-10\right)=0\)

\(\Rightarrow\left(3x-1\right)\left(x-10\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}3x-1=0\\x-10=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{1}{3}\\x=10\end{array}\right.\)

b)

\(x\left(x+7\right)-\left(4x+28\right)=0\)

\(\Rightarrow x\left(x+7\right)-4\left(x+7\right)=0\)

\(\Rightarrow\left(x-4\right)\left(x+7\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=4\\x=-7\end{array}\right.\)

c)

\(x\left(x-4\right)=2x-8\)

\(\Rightarrow x\left(x-4\right)-2\left(x-4\right)=0\)

\(\Rightarrow\left(x-4\right)\left(x-2\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=4\\x=2\end{array}\right.\)

d)

\(\left(2x+3\right)\left(x-1\right)+\left(2x+3\right)\left(x-1\right)=0\)

\(\Rightarrow2\left(2x+3\right)\left(x-1\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}2x+3=0\\x-1=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=-\frac{3}{2}\\x=1\end{array}\right.\)