bài 3 :tìm x a,4^x+4^x+1=320 b,5^x.5^3=-(15-40) c,2x^2-15=1 d,1762-(4X+3)=-5 e,(x^2+1)(x^2-1)=0

Question

bài 3 :tìm x
a,4^x+4^x+1=320
b,5^x.5^3=-(15-40)
c,2x^2-15=1
d,1762-(4X+3)=-5
e,(x^2+1)(x^2-1)=0

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Eden 5 tháng 2021-07-21T09:36:40+00:00 1 Answers 78 views 0

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    0
    2021-07-21T09:38:03+00:00

    a, $4^x+4^{x+1}=320$

    $=>4^x.(1+4)=320$

    $=>4^x.5=320$

    $=>4^x=64$

    $=>4^x=4^3$

    $=>x=3$

    b, $5^x.5^3=-(15-40)$

    $=>5^x.125=25$

    $=>5^x=$$\frac{1}{5}$ 

    $=>5^x=5^{-1}$

    $=>x=-1$

    c, $2x^2-15=1$

    $=>2x^2=16$

    $=>x^2=4$

    $=>x^2=2^2$

    $=>x=2$

    d, $1762-(4x+3)=-5$

    $=>4x+3=1767$

    $=>4x=1764$

    $=>x=441$

    e, $(x^1+1)(x^2-1=0$

    $=>x^2-1=0$

    $=>x^2=1$

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

    Vậy x=1, x=-1

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