meili 发表于 2022-10-27 15:09:26

已知x,y,z均为非负数,且满足x=y+z-1,x=4-y-2z,则u=2x2-2y-z的最大值为-12-12;最小值为______.

<p>问题:已知x,y,z均为非负数,且满足x=y+z-1,x=4-y-2z,则u=2x2-2y-z的最大值为-12-12;最小值为______.
<p>答案:↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">韩忠愿的回答:<div class="content-b">网友采纳  联立x=y+z−1x=4−y−2z,解得y=3x−2z=3−2x,∵x,y,z均为非负数,∴3x−2≥0①3−2x≥0②,解不等式①得,x≥23,解不等式②得,x≤32,∴23≤x≤32,u=2x2-2y-z,=2x2-2(3x-2)-(3-2x),=2x2-4x+1,=2(...
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