giúp mik vsssssssssss

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giúp mik vsssssssssss
giup-mik-vsssssssssss

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RI SƠ 1 year 2020-10-14T02:16:50+00:00 2 Answers 92 views 0

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    0
    2020-10-14T02:18:02+00:00

    Đáp án:

      bài 3:

    `a)102+2(x-3)=108`

    `⇔2(x-3)=108-102`

    `⇔2(x-3)=6`

    `⇔x-3=3`

    `⇔x=6`

    `b) [(x^2+2)+17]:5=20`

    `⇔x^2+2+17=20.5`

    `⇔x^2+19=100`

    `⇔x^2=100-19`

    `⇔x^2=81`

    `⇔x=+-9`

    `c) (x-1)^4=81`

    Th1: `(x-1)^4=3^4⇔x-1=3⇔x=4`

    Th2: `(x-1)^4=(-3)^4⇔x-1=-3⇔x=-2`

    bài 4:

    `A=1+4+4^2+4^3+…+4^100`

    `4A=4+4^2+4^3+…+4^101`

    `4A-A=(4+4^2+…+4^101)-(1+4+4^2+…+4^100)`

    `3A=4^101-1`

    `A=(4^101-1)/3`

    khi đó:

    `B=(4^101-1)/3-A=(4^101-1)/3-(4^101-1)/3=0`

    vậy `B=0`

    0
    2020-10-14T02:18:49+00:00

    bài 3:

    a) $102+2(x-3)=108$

    $↔2(x-3)=108-102=6$

    $↔x-3=6:2=3$

    $↔x=3+3=6$

    b) $[(x^2+2)+17]:5=20$

    $↔(x^2+2)+17=20.5=100$

    $↔x^2+2=100-17=83$

    $↔x^2=83-2=81$

    \(↔\left[ \begin{array}{l}x=9\\x=-9\end{array} \right.\)

    c) $(x-1)^4=81$

    \(↔\left[ \begin{array}{l}x-1=3\\x-1=-3\end{array} \right.\) $\to$ \(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\)

    Bài 4:

    $A=1+4+4^2+4^3+…+4^{100}$

    $4A=4+4^2+4^3+…+4^{101}$

    $4A-A=(4+4^2+4^3+…+4^{101})-(1+4+4^2+…+4^{100}$

    $3A=4^{101}-1$

    $→A=\dfrac{4^{101}-1}{3}$

    $→B=(4^{101}-1):3-A=\dfrac{4^{101}-1}{3}-\dfrac{4^{101}-1}{3}=0$

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