Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
1,\\
2\sqrt {3a} - \sqrt {75a} + \frac{1}{2}\sqrt {48a} \\
= 2\sqrt {3a} - \sqrt {{5^2}.3a} + \frac{1}{2}.\sqrt {{4^2}.3a} \\
= 2\sqrt {3a} - 5\sqrt {3a} + \frac{1}{2}.4.\sqrt {3a} \\
= 2\sqrt {3a} - 5\sqrt {3a} + 2\sqrt {3a} \\
= - \sqrt {3a} \\
2,\\
5\sqrt {8x} - \sqrt {4y} + \sqrt {18x} - \sqrt {9y} \\
= 5.\sqrt {{2^2}.2x} - \sqrt {{2^2}.y} + \sqrt {{3^2}.2x} - \sqrt {{3^2}.y} \\
= 5.2\sqrt {2x} - 2\sqrt y + 3.\sqrt {2x} - 3.\sqrt y \\
= 10\sqrt {2x} - 2\sqrt y + 3\sqrt {2x} - 3\sqrt y \\
= 13\sqrt {2x} - 5\sqrt y
\end{array}\)
