Bài 1: Tìm x, biết: a, x : (-1/2) mũ 2= 1/2 b, (2/5) mũ 7 . x = (2/5) mũ 10 c, (3x – 2) mũ 5 = 0 d, (x – 1/3) mũ 2 = 35/36 e, (4x + 1) mũ 3 = -125 g,

0 bình luận về “Bài 1: Tìm x, biết: a, x : (-1/2) mũ 2= 1/2 b, (2/5) mũ 7 . x = (2/5) mũ 10 c, (3x – 2) mũ 5 = 0 d, (x – 1/3) mũ 2 = 35/36 e, (4x + 1) mũ 3 = -125 g,”

1.  

   Bình luận

2. Đáp án:

    $a)
   x=\dfrac{1}{8}\\
   b)
   x=\left ( \dfrac{2}{5} \right )^{3}\\
   c)
    x=\dfrac{2}{3}\\
   d){\left[\begin{aligned}x=\dfrac{\sqrt{35}+2}{6}\\x=\dfrac{-\sqrt{35}+2}{6}\end{aligned}\right.}\\
   e)
    x=\dfrac{-3}{2}\\
   g)  {\left[\begin{aligned}x=\dfrac{-4}{25}\\x=\dfrac{-6}{25}\end{aligned}\right.}\\$

   Giải thích các bước giải:

    $a)
   x:\left ( -\dfrac{1}{2} \right )^2=\dfrac{1}{2}\\
   \Leftrightarrow x=\dfrac{1}{2}.\dfrac{1}{4}=\dfrac{1}{8}\\
   b)
   \left ( \dfrac{2}{5} \right )^7.x=\left ( \dfrac{2}{5} \right )^{10}\\
   \Leftrightarrow x=\left ( \dfrac{2}{5} \right )^{10}:\left ( \dfrac{2}{5} \right )^{7}\\
   \Leftrightarrow x=\left ( \dfrac{2}{5} \right )^{3}\\
   c)
   (3x-2)^5=0\\
   \Leftrightarrow 3x-2=0\\
   \Leftrightarrow 3x=2\\
   \Leftrightarrow x=\dfrac{2}{3}\\
   d)\left ( x-\dfrac{1}{3} \right )^2=\dfrac{35}{36}\\
   \Leftrightarrow x-\dfrac{1}{3}=\pm \dfrac{\sqrt{35}}{6}\\
   \Leftrightarrow {\left[\begin{aligned}x-\dfrac{1}{3}=\dfrac{\sqrt{35}}{6}\\x-\dfrac{1}{3}=-\dfrac{\sqrt{35}}{6}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}x=\dfrac{\sqrt{35}}{6}+\dfrac{1}{3}\\x=-\dfrac{\sqrt{35}}{6}+\dfrac{1}{3}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}x=\dfrac{\sqrt{35}+2}{6}\\x=\dfrac{-\sqrt{35}+2}{6}\end{aligned}\right.}\\
   e)
   (4x+1)^3=-125\\
   \Leftrightarrow 4x+1=-5\\
   \Leftrightarrow 4x=-5-1\\
   \Leftrightarrow 4x=-6\\
   \Leftrightarrow x=\dfrac{-3}{2}\\
   g) (5x+1)^2=\dfrac{1}{25}\\
   \Leftrightarrow {\left[\begin{aligned}5x+1=\dfrac{1}{5}\\5x+1=-\dfrac{1}{5}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}5x=\dfrac{1}{5}-1\\5x=-\dfrac{1}{5}-1\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}5x=\dfrac{-4}{5}\\5x=\dfrac{-6}{5}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}x=\dfrac{-4}{25}\\x=\dfrac{-6}{25}\end{aligned}\right.}\\$

   Bình luận