Toán Lớp 7: Tìm GTNN
C=|4x-3|+|5y+7,5|+17,5
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Toán Lớp 7: Tìm GTNN
C=|4x-3|+|5y+7,5|+17,5
Comments ( 2 )
|4x-3|ge0forallx
|5y+7,5|ge0forally
=>|4x-3|+|5y+7,5|ge0
=>|4x-3|+|5y+7,5|+17,5ge17,5
=>Cge17,5
Dấu = xảy ra khi:
{(|4x-3|=0),(|5y+7,5|=0):}
=>{(\text{4x-3=0}),(\text{5y+7,5=0} ):}
=>{(\text{4x=3}),(\text{5y=-7,5}):}
=>{(x=3/4),(y=-3/2):}
Vậy C_(min)=17,5 khi và chỉ khi x=3/4;y=-3/2