a) \(2401\cdot\left(\dfrac{1}{7}\right)^2\cdot\dfrac{1}{7}\cdot49^2\)
\(=7^4\cdot\left(\dfrac{1}{7}\right)^3\cdot7^4\)
\(=7^8\cdot\left(\dfrac{1}{7}\right)^3\)
\(=7^8\cdot\dfrac{1}{7^3}\)
\(=\dfrac{7^8}{7^3}\)
\(=7^5\)
b) \(9\cdot81:\left(3^3\cdot\dfrac{1}{27}\right)\)
\(=9\cdot9^2:\left(\dfrac{3^3}{3^3}\right)\)
\(=9^3:1\)
\(=9^3\)
c) \(3^4\cdot7^2\cdot\left(-\dfrac{7}{3}\right)^4\)
\(=3^4\cdot7^2\cdot\dfrac{7^4}{3^4}\)
\(=\dfrac{3^4\cdot7^2\cdot7^4}{3^4}\)
\(=7^2\cdot7^4\)
\(=7^6\)
a: =7^4*1/7^3*7^4=7^5
b: =3^2*3^4:3^2=3^4
c: =3^4*7^2*7^4/3^4=7^6