tìm x biết: a) (x-5)^2 = (1-3x)^2 b) x^2 + x = 0 c) 3^4 x 3^n = 3^7 mong các bn giúp mn thật nhanh vì mn đg cần gấp

Question

tìm x biết:
a) (x-5)^2 = (1-3x)^2
b) x^2 + x = 0
c) 3^4 x 3^n = 3^7
mong các bn giúp mn thật nhanh vì mn đg cần gấp

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Everleigh 1 năm 2021-09-18T13:41:52+00:00 2 Answers 7 views 0

Answers ( )

    0
    2021-09-18T13:43:35+00:00

    $a$) $(x-5)^2= (1-3x)^2$

    $⇒$ \(\left[ \begin{array}{l}x-5=1-3x\\x-5=-(1-3x)\end{array} \right.\) 

    $⇔$ \(\left[ \begin{array}{l}x+3x=1+5\\x-5=-1+3x)\end{array} \right.\) 

    $⇔$ \(\left[ \begin{array}{l}4x=6\\x-3x=-1+5)\end{array} \right.\) 

    $⇔$ \(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=-2)\end{array} \right.\) 

        Vậy $x$ $∈$ `{\frac{3}{2};-2}`

    $b$) $x^2+x=0$

    $⇔ x.(x+1)=0$

    $⇒$ \(\left[ \begin{array}{l}x=0\\x=-1\end{array} \right.\) 

       Vậy $x$ $∈$ {$0;-1$}

    $c$) $3^4 x 3^n = 3^7$

    $⇔ 3^{4+n} = 3^7$

    $⇔ 4+n=7$

    $⇔ n=3$

      Vậy $n=3$.

    0
    2021-09-18T13:43:41+00:00

    `a,` `(x-5)^2=(1-3x)^2`

    `⇒x-5=±(1-3x)`

    \(⇒\left[ \begin{array}{l}x-5=1-3x⇒4x=6⇒x=1,5\\x-5=3x-1⇒-2x=4⇒x=-2\end{array} \right.\)

    `Vậy` `x∈{1,5;-2}`

    `b,` `x^2+x=0`

    `⇒x(x+1)=0`

    \(⇒\left[ \begin{array}{l}x=0\\x+1=0⇒x=-1\end{array} \right.\)

    `Vậy` `x∈{0;-1}`

    `c,` `3^4 . 3^n=3^7`

    `⇒3^{4+n}=3^7`

    `⇒4+n=7`

    `⇒n=3`

    `Vậy` `n=3`

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