x^2+y^2-xy-3x-3y+9=0

Question

x^2+y^2-xy-3x-3y+9=0

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Ben Gia 4 years 2021-05-24T18:42:31+00:00 1 Answers 20 views 0

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  1. Nho
    0
    2021-05-24T18:44:24+00:00
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    Đáp án:

    (x;y)=(3;3)

    Giải thích các bước giải:

     Ta có:

    x2+y2–xy–3x–3y+9=0⇔2x2+2y2–2xy–6x–6y+18=0⇔(x2–2xy+y2)+(x2–6x+9)+(y2–6y+9)=0⇔(x–y)2+(x–3)2+(y–3)2=0⇔(x–y)2=(x–3)2=(y–3)2=0(do:(x–y)2+(x–3)2+(y–3)2≥0,∀x,y,z)⇔x–y=x–3=y–3=0⇔x=y=3

    Vậy (x;y)=(3;3)

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )