How to get the complete square ?

Questions
1

Why this simple case cannot be simplified to Complete Square form

Open in Wolfram Cloud ↗
2

Hi Yuhai,

The problem is that Subsuperscript is just notation, there is no Power in the expression. Use Power instead.

eq = 1/4 Subscript[n, 1]^4 + 1/2 Subscript[n, 2]^2 Subscript[n, 1]^2 + 1/4 Subscript[n, 2]^4
Simplify@eq
\frac{1}{4} \left(n_1^2+n_2^2\right){}^2
3

Thanks.