Tìm đkxđ 1, y= 4sin 3x/2x+1 2, y=-1/√x^2 – 3x + 2 3,y= 5cot(3x-π/3)

Đáp án:

$1) x\neq \dfrac{-1}{2}\\
2)  {\left[\begin{aligned}x\neq 1\\x\neq 2\end{aligned}\right.}\\
3) x\neq \dfrac{\pi}{9}+\dfrac{k\pi}{3},(k\in\mathbb{Z}) \\$

Giải thích các bước giải:

 $1) y=4\sin\dfrac{3x}{2x+1}\\
ĐK: 2x+1\neq 0\Leftrightarrow 2x\neq -1\Leftrightarrow x\neq \dfrac{-1}{2}\\
2) y=\dfrac{-1}{\sqrt{x^2-3x+2}}\\
ĐK: x^2-3x+2\neq 0\Leftrightarrow {\left[\begin{aligned}x\neq 1\\x\neq 2\end{aligned}\right.}\\
3) y=5\cot(3x-\dfrac{\pi}{3})\\
ĐK: 3x-\dfrac{\pi}{3}\neq k\pi\\
\Leftrightarrow 3x\neq \dfrac{\pi}{3}+k\pi\\
\Leftrightarrow x\neq \dfrac{\pi}{9}+\dfrac{k\pi}{3},(k\in\mathbb{Z}) \\$