Đáp án:
C=−2|x−y+1|−3|y−2|−4C=-2|x-y+1|-3|y-2|-4
Ta có:
−2|x−y+1|≤0∀x,y-2|x-y+1|≤0∀x,y
−3|y−2|≤0∀y-3|y-2|≤0∀y
⇒−2|x−y+1|−3|y−2|≤0⇒-2|x-y+1|-3|y-2|≤0
⇒−2|x−y+1|−3|y−2|−4≤−4⇒-2|x-y+1|-3|y-2|-4≤-4
Dấu = xảy ra ⇔⇔{y−2=0x−y+1=0{y−2=0x−y+1=0 ⇔⇔{y=2x=1{y=2x=1
Vậy Cmax=−4⇔x=1;y=2Cmax=-4⇔x=1;y=2.
