Question

Tìm x.

a) 3x (2x-5 )-4 (5-2x ) =0

b) x² + 3x=0

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

d) 4x² -9x+5=0

e) x(x-2)+x-2=0

2x² -5x+3=0

 

Answer 1

e, x(x - 2) + x - 2 = 0

=> (x-1)(x-2) = 0

=> x - 1 = 0 hoặc x - 2 = 0

=> x = 1 hoặc x = 2

vậy_

b, x² + 3x = 0

=> x(x + 3) = 0

=> x = 0 hoặc x + 3 = 0

=> x = 0 hoặc x = -3

vậy_

2x² - 5x + 3 = 0

=> 2.x.x - 5.x = -3

=> x(2x - 5) = -3

đoạn này lập bảng

d) 4x² - 9x + 5 = 0

=> 4.x.x - 9.x = -5

=> x(4x - 9) = -5

đến đây cx lập bảng 

Answer 2

bạn suy ngĩ kĩ trước khi đăng câu hỏi lên

Answer 3

\(a,3x\left(2x-5\right)-4\left(5-2x\right)=0\)

\(\Rightarrow3x\left(2x-5\right)+4\left(2x-5\right)=0\)

\(\Rightarrow\left(3x+4\right)\left(2x-5\right)=0\)

\(\Rightarrow\orbr{\begin{cases}3x+4=0\\2x-5=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{-4}{3}\\x=\frac{5}{2}\end{cases}}}\)

Vậy...

\(b,x^2+3x=0\)

\(\Rightarrow x\left(x+3\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}\orbr{\begin{cases}x=0\\x=-3\end{cases}}}\)

Vậy...

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

\(\Rightarrow3x\left(x+2\right)-\left(x+2\right)=0\)

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

\(\Rightarrow\orbr{\begin{cases}3x-1=0\\x+2=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{1}{3}\\x=-2\end{cases}}}\)

Vậy...

\(d,4x^2-9x+5=0\)

\(\Rightarrow4x^2-4x-5x+5=0\)

\(\Rightarrow4x\left(x-1\right)-5\left(x-1\right)=0\)

\(\Rightarrow\left(4x-5\right)\left(x-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}4x-5=0\\x-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{5}{4}\\x=1\end{cases}}}\)

Vậy...

\(e,x\left(x-2\right)+x-2=0\)

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

\(\Rightarrow\orbr{\begin{cases}x+1=0\\x-2=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-1\\x=2\end{cases}}}\)

Vậy...

\(g,2x^2-5x+3=0\)

\(\Rightarrow2x^2-2x-3x+3=0\)

\(\Rightarrow2x\left(x-1\right)-3\left(x-1\right)=0\)

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

\(\Rightarrow\orbr{\begin{cases}2x-3=0\\x-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{3}{2}\\x=1\end{cases}}}\)

Vậy...

Answer 4

a) \(3x\left(2x-5\right)-4\left(5-2x\right)=0\)

\(\Rightarrow3x\left(2x-5\right)+4\left(2x+5\right)=0\)

\(\Rightarrow\left(2x-5\right)\left(3x+4\right)=0\)

\(\Rightarrow\orbr{\begin{cases}2x-5=0\\3x+4=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}2x=5\\3x=-4\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{5}{2}\\x=\frac{-4}{3}\end{cases}}\)

b) \(x^2+3x=0\)

\(\Rightarrow x\left(x+3\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}}\)

c)  \(3x\left(x+2\right)-x-2=0\)

\(\Rightarrow3x\left(x+2\right)-x+2=0\)

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

\(\Rightarrow\orbr{\begin{cases}x+2=0\\3x+1=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=-2\\x=\frac{-1}{3}\end{cases}}\)

d) \(4x^2-9x+5=0\)

\(\Rightarrow4x^2-4x-5x+5=0\)

\(\Rightarrow\left(4x^2-4x\right)-\left(5x-5\right)\)

\(\Rightarrow4x\left(x-1\right)-5\left(x-1\right)\)

\(\Rightarrow\left(x-1\right)\left(4x-5\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-1=0\\4x-5=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\4x=5\end{cases}}\Rightarrow\orbr{\begin{cases}x=1\\x=\frac{5}{4}\end{cases}}\)

e) \(x\left(x-2\right)+x-2=0\)

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

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

\(\Rightarrow\orbr{\begin{cases}x-2=0\\x+1=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=-1\end{cases}}\)

f) \(2x^2-5x+3=0\)

\(\Rightarrow2x^2-2x-3x+3=0\)

\(\Rightarrow\left(2x^2-2x\right)-\left(3x-3\right)=0\)

\(\Rightarrow2x\left(x-1\right)-3\left(x-1\right)=0\)

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

\(\Rightarrow\orbr{\begin{cases}x-1=0\\2x-3=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\2x=3\end{cases}}\Rightarrow\orbr{\begin{cases}x=1\\x=\frac{3}{2}\end{cases}}\)

Answer 5

a) \(3x\left(2x-5\right)-4\left(5-2x\right)=0\)

\(\Leftrightarrow3x\left(2x-5\right)+4\left(2x-5\right)=0\)

\(\Leftrightarrow\left(2x-5\right)\left(3x+4\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-5=0\\3x+4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{5}{2}\\x=\frac{-4}{3}\end{cases}}}\)     Vậy \(x=\frac{5}{2};x=\frac{-4}{3}\)

b)\(x^2+3=0\)

\(\Leftrightarrow x\left(x+3\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}}\) Vậy:.........

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

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

\(\Leftrightarrow\orbr{\begin{cases}x+2=0\\3x-1=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-2\\x=\frac{1}{3}\end{cases}}\) Vậy:...............

d)\(4x^2-9x+5=0\)

\(\Leftrightarrow4x^2-4x-5x+5=0\)

\(\Leftrightarrow4x\left(x-1\right)-5\left(x-1\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(4x-5\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\4x-5=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\x=\frac{5}{4}\end{cases}}\) Vậy:....................

e) \(x\left(x-2\right)+x-2=0\)

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

\(\Leftrightarrow\orbr{\begin{cases}x-2=0\\x+1=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=2\\x=-1\end{cases}}\) Vậy:...................

f) \(2x^2-5x+3=0\)

\(\Leftrightarrow2x^2-2x-3x+3=0\)

\(\Leftrightarrow2x\left(x-1\right)-3\left(x-1\right)=0\)

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

\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\2x-3=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\x=\frac{3}{2}\end{cases}}\) Vậy:...............