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

Toán Lớp 8: A=$x^{5}$ – 100 $x^{4}$ +100 $x^{3}$ -100 $x^{2}$ +100x – 9 tại x=99 B=x $x^{6}$ – 20 $x^{5}$ – 20 $x^{4}$ – 20x $x^{3}$ – 20 $x^{2}$ –

Toán Lớp 8: A=$x^{5}$ – 100 $x^{4}$ +100 $x^{3}$ -100 $x^{2}$ +100x – 9 tại x=99
B=x $x^{6}$ – 20 $x^{5}$ – 20 $x^{4}$ – 20x $x^{3}$ – 20 $x^{2}$ -20x + 3 tại x=21
Tính hợp lí nha, cần gấp

Comments ( 2 )

  1. Đáp án:
     
    Giải thích các bước giải:
     

    toan-lop-8-a-5-100-4-100-3-100-2-100-9-tai-99-b-6-20-5-20-4-20-3-20-2

  2. $\\$
    a,
    x=99
    => x+1=100
    A=x^5 – 100x^4 + … + 100x – 9
    => A=x^5 – (x+1)x^4 + … +(x+1)x-9
    =>A=x^5 -x^5 – x^4 + … +x^2 +x-9
    =>A=(x^5 – x^5) + … + (-x^2 +x^2)+(x-9)
    =>A=x-9
    =>A=99-9=90
    Vậy A=90
    $\\$
    x=21
    =>x-1=20
    B=x^6 – 20x^5 – … – 20x +3
    =>B=x^6 – (x-1)x^5 – … – (x-1)x +3
    =>B=x^6 – x^6 + x^5 – … – x^2 +x+3
    =>B = (x^6 – x^6) + … + (x^2 – x^2)+(x+3)
    =>B=x+3 = 21 +3=24
    Vậy B=24

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