giúp mình nhé

Question

Tính bằng hai cách:

a)(1/4+1/7)x1/3

b)(1/4-1/7)x1/3

Answer 1

\( C_1: \bigg(\dfrac{1}{4}+\dfrac{1}{7}\bigg) \times \dfrac{1}{3}\\=\dfrac{11}{28} \times \dfrac{1}{3}\\=\dfrac{11}{84}\)
\(C_2: \bigg(\dfrac{1}{4}+\dfrac{1}{7}\bigg)\times\dfrac{1}{3}\\=\dfrac{1}{4}\times\dfrac{1}{3}+\dfrac{1}{7}\times\dfrac{1}{3}\\=\dfrac{1}{12}+\dfrac{1}{21}=\dfrac{11}{84} \)
Tương tự với câu b)