Question

rất gấp ạ

Answer 1

a)

\(C=\dfrac{15^3+5\cdot15^2-5^3}{18^3+6\cdot18^2-6^3}=\dfrac{3^3\cdot5^3+5\cdot5^2\cdot3^2-5^3}{3^3\cdot6^3+6\cdot6^2\cdot3^2-6^3}\)

\(C=\dfrac{3^3\cdot5^3+5^3\cdot3^2-5^3}{3^3\cdot6^3+6^3\cdot3^2-6^3}\)

\(C=\dfrac{5^3\left(3^3+3^2-1\right)}{6^3\left(3^3+3^2-1\right)}\)

\(C=\dfrac{5^3}{6^3}=\dfrac{125}{216}\)

b)

\(D=\dfrac{\left(7^4-7^3\right)^3}{49^3}\)

\(D=\left(\dfrac{7^4-7^3}{7^2}\right)^3\)

\(D=\left\{\dfrac{7^3\left(7-1\right)}{7^2}\right\}^3\)

\(D=\left(7\cdot6\right)^3=42^3=74088\)