Question

calcule x:
a) x^3=7^9

Answer 1

$\sqrt[m]{x^n} \ \ \textless \ =\ \textgreater \ x ^\frac{m}{n} \\ \\ \\ x^3 = 7^9 \\ \\ x = \sqrt[3]{7^9}$

$x = 7^ \frac{9}{3} \\ \\ x = 7^3 =\ \textgreater \ 343$

Answer 2

x³ = 7⁹
x = ∛7⁹ = ∛(7³)³
x = 7³ 
x = 343

Realmente, x=343, veja: 

343³ = 7⁹
(7³)³ = 7⁹
7⁹ = 7⁹