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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 11: Tìm GTNN,GTLN của :y=3-2sin(2x+1)

Toán Lớp 11: Tìm GTNN,GTLN của :y=3-2sin(2x+1)

Comments ( 2 )

  1. Ta có: $\sin x \in [-1;1]$
    $⇔ -1 \le \sin x \le 1$
    $⇔ -1 \le \sin (2x+1) \le 1$
    $⇔ -2 \le 2 \sin (2x+1) \le 2$
    $⇔ 5 \ge 3-2 \sin (2x+1) \ge 1$
    $\max = 5$ khi $2x+1 = -\dfrac{\pi}{2}+k2\pi ⇔ x=-\dfrac{3\pi}{4}+k\pi \ (k \in \mathbb{Z})$
    $\min = 1$ khi $2x+1 = \dfrac{\pi}{2}+k2\pi ⇔ x = -\dfrac{\pi}{4}+k\pi \ (k \in \mathbb{Z})$

  2. $-1≤sin(2x+1)≤1$
    $⇔2≥-2sin(2x+1)≥-2$
    $⇔5≥3-2sin(2x+1)≥1$
    Vậy $GTLN:y=5$
    $GTNN:y=1$
     

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222-9+11+12:2*14+14 = ? ( )

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