
1) $$ \sqrt{100c^6} = \sqrt{100} \cdot \sqrt{c^6} = 10 \cdot |c^3| $$.
Так как $$ c \leq 0 $$, то $$ |c^3| = -c^3 $$.
$$ 10 \cdot |c^3| = -10c^3 $$.
2) $$ \sqrt{9m^4n^{34}} = \sqrt{9} \cdot \sqrt{m^4} \cdot \sqrt{n^{34}} = 3m^2n^{17} $$.
3) $$ \sqrt{0,16a^{38}b^{42}} = \sqrt{0,16} \cdot \sqrt{a^{38}} \cdot \sqrt{b^{42}} = 0,4 \cdot a^{19} \cdot |b^{21}| $$.
Так как $$ b \leq 0 $$, то $$ |b^{21}| = -b^{21} $$.
$$ 0,4 \cdot a^{19} \cdot |b^{21}| = -0,4a^{19}b^{21} $$.
4) $$ \sqrt{\frac{x^{20}y^{46}z^{50}}{x^8y^9z^{12}}} = \sqrt{x^{20-8}y^{46-9}z^{50-12}} = \sqrt{x^{12}y^{37}z^{38}} = x^6 \cdot |y^{18}| \cdot |z^{19}| \cdot \sqrt{y} $$.
Так как $$ y > 0 $$, то $$ |y^{18}| = y^{18} $$.
Так как $$ z < 0 $$, то $$ |z^{19}| = -z^{19} $$.
$$ x^6 \cdot |y^{18}| \cdot |z^{19}| \cdot \sqrt{y} = -x^6y^{18}z^{19}\sqrt{y} $$.
5) $$ \frac{3,5a^{15}}{b^{10}} \cdot \sqrt{\frac{b^{24}}{0,25a^{26}}} = \frac{3,5a^{15}}{b^{10}} \cdot \frac{\sqrt{b^{24}}}{\sqrt{0,25a^{26}}} = \frac{3,5a^{15}}{b^{10}} \cdot \frac{b^{12}}{0,5a^{13}} = \frac{3,5}{0,5} \cdot \frac{a^{15}}{a^{13}} \cdot \frac{b^{12}}{b^{10}} = 7a^2b^2 $$.
6) $$-0,6c^7 \cdot \sqrt{1,44b^{12}c^{14}} = -0,6c^7 \cdot \sqrt{1,44} \cdot \sqrt{b^{12}} \cdot \sqrt{c^{14}} = -0,6c^7 \cdot 1,2 \cdot |b^6| \cdot |c^7| $$.
Так как $$ c \leq 0 $$, то $$ |c^7| = -c^7 $$.
$$ -0,6c^7 \cdot 1,2 \cdot |b^6| \cdot |c^7| = 0,72c^{14}b^6 $$.
Ответ: 1) $$-10c^3$$; 2) $$3m^2n^{17}$$; 3) $$-0,4a^{19}b^{21}$$; 4) $$-x^6y^{18}z^{19}\sqrt{y}$$; 5) $$7a^2b^2$$; 6) $$0,72c^{14}b^6$$.