Question

Tìm x biết

a.2(x-1)-3(2x+2)-4(2x+3)=16

b. \(3\dfrac{1}{2}:\left|2x-1\right|=\dfrac{21}{22}\)

c.\(\dfrac{2x-y}{5}=\dfrac{3x-2z}{15}\)và x+z=2y

Answer 1

Câu a)

\(2\left(x-1\right)-3\left(2x+2\right)-4\left(2x+3\right)=16\)

\(\Leftrightarrow2x-2-6x-6-8x-12=16\)

\(\Leftrightarrow-12x-20=16\)

\(\Leftrightarrow-12x=16+20\)

\(\Leftrightarrow-12x=36\)

\(\Leftrightarrow x=-3\)

Vậy \(x=-3\)

Answer 2

Câu c)

\(\dfrac{2x-y}{5}=\dfrac{3x-2z}{15}\) \(\Rightarrow\dfrac{3\left(2x-y\right)}{3\times5}=\dfrac{3x-2z}{15}\) \(\Rightarrow\dfrac{6x-3y}{15}=\dfrac{3x-2z}{15}\)

\(\Rightarrow6x-3y=3x-2z\)

\(\Rightarrow6x-3x+2z=3y\)

\(\Rightarrow3x+2z=3y\)

\(\Rightarrow\left(2x+2z\right)+x=3y\)

\(\Rightarrow2\left(x+z\right)+x=3y\)

\(\Rightarrow2\times2y+x=3y\)

\(\Rightarrow4y+x=3y\)

\(\Rightarrow x=3y-4y\)

\(\Rightarrow x=-y\)