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

Toán Lớp 8: cho a,b>0 tm a+b<=6 tìm min P=5-2a/1+a +5-2b/1+b hd mk thôi cx đc ạ

Toán Lớp 8: cho a,b>0 tm a+b<=6 tìm min P=5-2a/1+a +5-2b/1+b hd mk thôi cx đc ạ

Comments ( 1 )

  1. #huy
    P=(5-2a)/(1+a) +(5-2b)/(1+b)
    =(7-2(a+1))/(a+1)+(7-1(b+1))/(b+1)
    =7(1/(a+1)+1/(b+1))-4
    Áp dụng 1/a+1/b>=4/(a+b) ta có:
    1/(a+1)+1/(b+1)>=4/(a+b+2)>=4/(6+2)=4/8=1/2
    =>P>=7 . 1/2-4=-1/2
    P_min=-1/2
     

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

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