Ta có:
S=\(\dfrac{\dfrac{5}{3}+\dfrac{5}{4}+\dfrac{5}{6}}{\dfrac{10}{6}+\dfrac{10}{8}+\dfrac{10}{12}}\)
S=\(\dfrac{5.\left(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{6}\right)}{5.\left(\dfrac{2}{6}+\dfrac{2}{8}+\dfrac{2}{12}\right)}\)
S=\(\dfrac{5.\left(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{6}\right)}{5\left(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{6}\right)}\)
S=1
Ta có: \(S=\dfrac{\dfrac{5}{3}+\dfrac{5}{4}+\dfrac{5}{6}}{\dfrac{10}{6}+\dfrac{10}{8}+\dfrac{10}{12}}=\dfrac{\dfrac{5}{3}+\dfrac{5}{4}+\dfrac{5}{6}}{\dfrac{5}{3}+\dfrac{5}{4}+\dfrac{5}{6}}=1\)
Cách 2:(ngắn hơn cách 1 nhưng cách 1 vẫn thông dụng hơn nhé!)
2S=\(\dfrac{2\left(\dfrac{5}{3}+\dfrac{5}{4}+\dfrac{5}{6}\right)}{\dfrac{10}{6}+\dfrac{10}{8}+\dfrac{10}{12}}\)(nhân 2 vào tử,giá trị tăng 2)
2S=\(\dfrac{\dfrac{10}{3}+\dfrac{10}{4}+\dfrac{10}{6}}{\dfrac{10}{6}+\dfrac{10}{8}+\dfrac{10}{12}}\)
S=\(\dfrac{\dfrac{10}{3}+\dfrac{10}{4}+\dfrac{10}{6}}{2\left(\dfrac{10}{6}+\dfrac{10}{8}+\dfrac{10}{12}\right)}\)(sau khi nhân 2 vào tử tiếp tục nhân vào mẫu để gt k thay đổi)
S=\(\dfrac{\dfrac{10}{3}+\dfrac{10}{4}+\dfrac{10}{6}}{\dfrac{10}{3}+\dfrac{10}{4}+\dfrac{10}{6}}\)=1
