To factor the given expression completely, we first look for common factors in each term. We notice that \(2u^2\) is a common factor in both terms. After factoring out \(2u^2\), we simplify the expression inside the parentheses.
Step 1: Identify Common Factors
The given expression is \(2u^2y^4 - 2u^2\). We first identify the common factor in both terms, which is \(2u^2\).
Step 2: Factor Out the Common Factor
We factor out \(2u^2\) from the expression:
\[
2u^2(y^4 - 1)
\]
Step 3: Recognize the Difference of Squares
The expression inside the parentheses, \(y^4 - 1\), is a difference of squares. It can be rewritten as:
\[
(y^2)^2 - 1^2
\]
This can be factored further using the difference of squares formula:
\[
(y^2 - 1)(y^2 + 1)
\]
Step 4: Factor the Difference of Squares Again
The term \(y^2 - 1\) is also a difference of squares:
\[
(y - 1)(y + 1)
\]
Step 5: Combine All Factors
Substituting back, the completely factored form of the original expression is:
\[
2u^2(y - 1)(y + 1)(y^2 + 1)
\]
Final Answer
The completely factored expression is:
\[
\boxed{2u^2(y - 1)(y + 1)(y^2 + 1)}
\]