Bài 3:
Áp dụng tính chất của dãy tỉ số bằng nhau,ta được:
\(\dfrac{x}{9}=\dfrac{y}{7}=\dfrac{z}{8}=\dfrac{z-y}{8-7}=8\)
Do đó: x=72; y=56; z=64
\(a,=\dfrac{1}{6}-\dfrac{7}{6}=-1\\ b,=-\dfrac{1}{6}\cdot6-\dfrac{5}{6}+4\cdot\dfrac{1}{4}=-1-\dfrac{5}{6}+1=-\dfrac{5}{6}\\ c,=\left[\left(\dfrac{4}{5}-\dfrac{2}{3}\right)\cdot\dfrac{5}{2}+\dfrac{1}{2}\right]\cdot\dfrac{3}{5}=\left(\dfrac{2}{15}\cdot\dfrac{5}{2}+\dfrac{1}{2}\right)\cdot\dfrac{3}{5}=\dfrac{5}{6}\cdot\dfrac{3}{5}=\dfrac{1}{2}\\ d,=\left(-\dfrac{8}{3}\right)\cdot\left(-3\dfrac{1}{6}\right)=\dfrac{8}{3}\cdot\dfrac{18}{6}=8\)
