a) Ta có: \(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{2}=k\)
\(\Rightarrow x=3k,y=5k,z=2k\)
Mà: \(xyz=810\)
\(\Rightarrow3k\cdot5k\cdot2k=30k^2=810\)
\(\Rightarrow k^2=\dfrac{810}{30}=9\)
\(\Rightarrow k=\sqrt{9}=3\)
Ta tìm được x, y, z:
\(x=3\cdot3=9,y=5\cdot3=15,z=2\cdot3=6\)
b: =>\(\dfrac{x+32}{11}-3+2-\dfrac{x+27}{14}=\dfrac{x+38}{13}-3+2-\dfrac{x+23}{12}\)
=>\(\left(x-1\right)\left(\dfrac{1}{11}-\dfrac{1}{14}\right)=\left(x-1\right)\cdot\left(\dfrac{1}{13}-\dfrac{1}{12}\right)\)
=>x-1=0
=>x=1
c: =>0,4x-4,5-3,2x+1,6-0,8+0,4x=3,2
=>-2,4x-3,7=3,2
=>-2,4x=6,9
=>x=-69/24=-23/8
