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

Toán Lớp 8: Tìm min: A = x^2 – 2xy + 3y^2 – 2x + 1997

Toán Lớp 8: Tìm min: A = x^2 – 2xy + 3y^2 – 2x + 1997

Comments ( 1 )

  1. Giải đáp:
     A=x²-2xy+3y²-2x+1977
    A=(x²+y²+1-2xy-2y+2x)+2y²+2y+1/8+1997-1-1/8
    A=(x-y+1)²+2(y²+y+1/4)+15967/8
    A=(x-y+1)²+2(y+1/2)²+15967/8≥15967/8
    Min A=15967/8 dấu “=” xảy ra khi y=-1/2 ; x=-3/2
    Lời giải và giải thích chi tiết:
     

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

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