Answer
$4x\sqrt[4] {x^3}$
Work Step by Step
$-2\sqrt[4] {x^7}+3\sqrt[4] {16x^7}$ Factor.
$-2\sqrt[4] {x^4}\sqrt[4] {x^3}+3\sqrt[4] {8x^4}\sqrt[4] {x^3}$ Simplify.
$-2x\sqrt[4] {x^3}+6x\sqrt[4] {x^3}$ Combine like terms.
$4x\sqrt[4] {x^3}$