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

Toán Lớp 8: rút gọn A= (ab+bc+ca)( 1/a + 1/b + 1/c) – abc( 1/a ² + 1/b ² + 1/c ²)

Tháng Năm 18, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: rút gọn A= (ab+bc+ca)( 1/a + 1/b + 1/c) – abc( 1/a ² + 1/b ² + 1/c ²)

Comments ( 2 )

  1. ngocle44
    ngocle44
    18 Tháng Năm, 2022 at 10:09 sáng
    Reply
    Gửi em:
    $ĐKXĐ:a,b,c\neq0$
    $A=(ab+bc+ca).(\dfrac{1}{c}+\dfrac{1}{a}+\dfrac{1}{c})-abc(\dfrac{1}{a^2}+\dfrac{1}{c^2}+\dfrac{1}{b^2})$ 
    $A=\dfrac{ab}{c}+\dfrac{bc}{a}+\dfrac{ca}{b}-abc(\dfrac{1}{a^2}+\dfrac{1}{c^2}+\dfrac{1}{b^2})$ 
    $A=\dfrac{ab}{c}+\dfrac{bc}{a}+\dfrac{ca}{b}-\dfrac{abc}{a^2}-\dfrac{abc}{c^2}-\dfrac{abc}{b^2}$
    $A=\dfrac{ab}{c}+\dfrac{bc}{a}+\dfrac{ca}{b}-\dfrac{bc}{a}-\dfrac{ab}{c}-\dfrac{ac}{b}$ 
    $A=\dfrac{ab}{c}-\dfrac{ab}{c}+\dfrac{bc}{a}-\dfrac{bc}{a}+\dfrac{ca}{b}-\dfrac{ac}{b}$ 
    $A=0-0-0$
    $A=0$ 
    Vậy $A=0.$
    $#vuatoanhoc#$
     

  2. kimoanh34
    kimoanh34
    18 Tháng Năm, 2022 at 10:09 sáng
    Reply
    =>b+a+ab/c+bc/a+c+b+c+ac/b+a-abc/a ² -abc/b ² -abc/c ²
    b+a+ab/c+bc/a+c+b+c+ac/b+a-ab/c-bc/a-ac/b
    =>2b+2a+2c=>2(a+b+c)=>đpcm

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

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