Question

Help pleaseee i dont understand

Answer 1

I think the 3rd one is the answer

Answer 2

In order to combine radicals when you're adding or subtracting, 2 things have to be in place. First, the index has to be the same. We have all the indices as 4's (fourth roots), so we're good there. Second, the radicand also has to be the same. Right now, none of them are, so we need to try to simplify and see if they are the same, just well-hidden. The first one, $2(\sqrt[4]{16x} )$ can be simplified down to $2(\sqrt[4]{2*2*2*2*x})$. We can pull out one of those 4 twos, and when we do that we have $2(2\sqrt[4]{x})$ which simplifies even further to $4\sqrt[4]{x}$. The second term, $-2(\sqrt[4]{2y})$ cannot be simplified at all...it is what it is. Next term, $3(\sqrt[4]{81x}$ can be rewritten as $3(\sqrt[4]{3*3*3*3*x})$. We can pull out one of those 4 threes and simplify to $3(3\sqrt[4]{x})$ which simplifies even further to $9\sqrt[4]{x}$. Lastly, we have $-4(\sqrt[4]{32y}$. We can rewrite this as $-4(\sqrt[4]{2*2*2*2*2*y})$. Pulling out 4 twos leaves us with $-4(2\sqrt[4]{2y}$ which simplifies to $-8\sqrt[4]{2y}$. So here's what we have in all: $4\sqrt[4]{x}-2\sqrt[4]{2y}+9\sqrt[4]{x}-8\sqrt[4]{2y}$. We will combine the like terms to get a final answer of $13\sqrt[4]{x}-10\sqrt[4]{2y}$. Third choice down is the one you want.