Question

I need help understanding square roots

Answer 1

I wonder if you mean to write $\sqrt[3]{256}$ in place of $3\sqrt{256}$...

If you meant what you wrote, then we have

$\sqrt{256}=\sqrt{16^2}=16$

$3\sqrt{256}=3\cdot16=48$

If you meant to write $\sqrt[3]{256}$ (the cube root of 256), then we could go on to have

$\sqrt[3]{256}=\sqrt[3]{16^2}=\sqrt[3]{(4^2)^2}=\sqrt[3]{4^4}=\sqrt[3]{4^3\cdot4}=4\sqrt[3]4$