Giải:
Ta có: \(\left\{x\in N|x^2+4^2=25\right\}\)
\(\Leftrightarrow x^2+4^2=25\)
\(\Leftrightarrow x^2+16=25\)
\(\Leftrightarrow x^2=25-16\)
\(\Leftrightarrow x^2=9\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-3\left(ktm\right)\\x=3\left(tm\right)\end{matrix}\right.\)
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