Tìm GTLN P = -|y+7|+49 Q = 2019-|3y-12|

0 bình luận về “Tìm GTLN P = -|y+7|+49 Q = 2019-|3y-12|”

1. a) Ta có: $|y+7|\geq 0\forall y$
   $\Leftrightarrow -|y+7|\leq 0\forall y$
   $\Leftrightarrow -|y+7|+49\leq 49\forall y$
   $\Leftrightarrow P\leq 49\forall y$
   Dấu “=” xảy ra khi $|y+7|=0\Leftrightarrow y=-7$
   Vậy $Max_{P}=49\Leftrightarrow y=-7$
   b) Ta có: $|3y-12|\geq 0\forall y$
   $\Leftrightarrow -|3y-12|\leq 0\forall y$
   $\Leftrightarrow 2019-|3y-12|\leq 2019\forall y$
   $\Leftrightarrow Q\leq 2019\forall y$
   Dấu “=” xảy ra khi $|3y-12|=0\Leftrightarrow y=4$
   Vậy $Max_{Q}=2019\Leftrightarrow y=4$

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2. BẠN THAM KHẢO NHA!

   BÀI LÀM:

    $P=-|y+7|+49$

   $-|y+7| \leq 0 \to -|y+7|+49 \leq 49 \to P\leq49 \to maxP=49$

   Dấu “=” xảy ra khi $-|y+7|=0 \to y=-7$

   $Q=2019-|3y-12|$

   $-|3y-12| \leq 0 \to 2019-|3y-12| \leq 2019 \to Q\leq2019 \to maxQ=2019$

   Dấu “=” xảy ra khi: $-|3y-12$=0 \to y=4$

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