\(\dfrac{1}{2}\sqrt{16a^2}-\sqrt{9a^2}\)
\(=\dfrac{1}{2}\sqrt{\left(4a\right)^2}-\sqrt{\left(3a\right)^2}\)
\(=\dfrac{1}{2}\left|4a\right|-\left|3a\right|\)
\(=\dfrac{1}{2}\left|a\right|\)
Nhầm ha.
\(\dfrac{1}{2}\sqrt{16a^2}-\sqrt{9a^2}\)
\(=\dfrac{1}{2}.4\left|a\right|-3\left|a\right|\)
\(=2\left|a\right|-3\left|a\right|\)
\(=-\left|a\right|\)