Question

1. Tính \(\dfrac{5^4.20^4}{25^5.4^5}\)

2. Tìm x :

a ) -x - \(\dfrac{2}{3}\) = \(\dfrac{-6}{7}\)

b ) \(\left|x+1\right|=2\)

c ) x² = 16

Answer 1

1:

\(\dfrac{5^4.20^4}{25^5.4^5}=\dfrac{100^4}{100^5}=\dfrac{1}{100}\)

2:

a)\(-x-\dfrac{2}{3}=-\dfrac{6}{7}\Rightarrow-x=-\dfrac{6}{7}+\dfrac{2}{3}=-\dfrac{4}{21}\Rightarrow x=\dfrac{4}{21}\)

b)

\(\left|x+1\right|=2\Rightarrow\left[{}\begin{matrix}x+1=2\\x+1=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=-3\end{matrix}\right.\)

c)

\(x^2=16\Rightarrow x=\pm4\)

Answer 2

1. \(\dfrac{5^4.20^4}{25^5.4^5}=\dfrac{\left(5.20\right)^4}{\left(25.4\right)^5}=\dfrac{100^4}{100^5}=\dfrac{100^4}{100.100^4}=\dfrac{1}{100}\)

2.a)\(-x-\dfrac{2}{3}=-\dfrac{6}{7}\)

\(-x=\dfrac{-6}{7}+\dfrac{2}{3}\)

\(-x=\dfrac{-18}{21}+\dfrac{14}{21}\)

\(-x=\dfrac{-4}{21}\)

\(x=-\left(-\dfrac{4}{21}\right)\)

\(x=\dfrac{4}{21}\)

b)\(\left|x+1\right|=2\)

Có 2 trường hợp: x+1=2 hoặc x+1= -2

*TH1: x+1=2

x=2-1

x=1

*TH2: x+1= -2

x= -2-1

x= -3

Vậy: x=1 hoặc x= -3

c)\(x^2=16\)

\(x^2=4^2\)

\(\Rightarrow x=4\)