tìm GTLN-GTNN

H

huynhbachkhoa23

Bài 1:

$y=\dfrac{3}{\tan^2 x+1}$

DK: $x\ne \dfrac{\pi}{2}$

$\dfrac{3}{y}-1=\tan^2 x \ge 0 \leftrightarrow \dfrac{3}{y} \ge 1 \leftrightarrow y \le 3$

$\text{max}y=3 \leftrightarrow x=0$
 
B

buivanbao123

3/ý= 3sin2x -2
Ta có:-1 \leg sin2x \leq 1
<=>-3 \leq 3Sin2x \leq 3
<=>-5 \leq 3sin2x-2 \leq 1
<=>-5 \leq y \leq 1
 
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