#### Answer

$25,281$

#### Work Step by Step

Substituting $a=1$ and $b=2$ in the given expression, $
a^{50}-20a^{25}b^4+100b^8
,$ results to
\begin{array}{l}\require{cancel}
a^{50}-20a^{25}b^4+100b^8
\\\\=
(1)^{50}-20(1)^{25}(2)^4+100(2)^8
\\\\=
(1)-20(1)(16)+100(256)
\\\\=
1-320+25600
\\\\=
25,281
.\end{array}