Đáp án:
C2:
g) \( - 6x - 2\)
Giải thích các bước giải:
\(\begin{array}{l}
C1:\\
a)DK:x \le 0\\
b)DK:x \ge 0\\
c)DK:x - 2021 \ge 0\\
\to x \ge 2021\\
d)DK:2020 - 4x \ge 0\\
\to 505 \ge x\\
C2:\\
a)3\sqrt 2 + 8\sqrt 2 - 3\sqrt 2 \\
= 8\sqrt 2 \\
c)\left( {2\sqrt 7 - 2\sqrt 3 + \sqrt 7 } \right).\sqrt 7 + 2\sqrt {21} \\
= 3.7 - 2\sqrt {21} + 2\sqrt {21} = 21\\
e)\dfrac{y}{x}.\dfrac{{\left| x \right|}}{{{y^2}}} = \dfrac{y}{x}.\dfrac{x}{{{y^2}}}\left( {Do:x > 0} \right)\\
= \dfrac{1}{y}\\
b)\left( {150\sqrt 2 - 45\sqrt 2 + 10\sqrt 2 } \right).\dfrac{1}{{\sqrt {10} }}\\
= 115\sqrt 2 .\dfrac{1}{{\sqrt {10} }} = \dfrac{{115}}{{\sqrt 5 }}\\
d)\dfrac{{\sqrt a \left( {\sqrt a + \sqrt b } \right)}}{{\sqrt a + \sqrt b }} = \sqrt a \\
g)\sqrt {4{{\left( {1 + 3x} \right)}^2}} \\
= 2\left| {3x + 1} \right| = - 2\left( {3x + 1} \right)\\
= - 6x - 2
\end{array}\)
