Tìm \(x\)
\(|x|+3=5\)
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Ta có:
\(x^2+\dfrac{1}{x^2}=4\)\(\left(x\ne0\right)\)
\(\left(x^2+\dfrac{1}{x^2}\right)^2=16\)
\(x^4+\dfrac{2.x^2}{x^2}+\dfrac{1}{x^4}=16\)
\(x^4+\dfrac{1}{x^4}=16-2=14\)
x² + 1/x² = 4
⇒ (x² + 1/x²)² = 16
⇒ x⁴ + 2.x².1/x² + 1/x⁴ = 16
⇒ x⁴ + 1/x⁴ + 2 = 16
⇒ x⁴ + 1/x⁴ = 16 - 2
⇒ x⁴ + 1/x⁴ = 14
3 I don't have a ladder
4 We didn't have enough time
5 He didn't have a map
6 She doesn't have any money
7 I don't have enough energy
8 They didn't have a camera
donate: book, fresh water, old clothes, water, food, money
clean: shool yard, houses, parks, streets, buildings
help: elderly people, homeless people, street children, poor people
repair: houses, streets, schoolyard, buildings
\(9:27^x=\dfrac{1}{18}\)
\(\Rightarrow9:\left(3^3\right)^x=\dfrac{1}{18}\)
\(\Rightarrow3^{3x}=9:\dfrac{1}{18}\)
\(\Rightarrow3^{3x}=162\)
Xem lại đề
\(\left|x\right|+3=5\)
\(\Rightarrow\left|x\right|=5-3\)
\(\Rightarrow\left|x\right|=2\)
\(\Rightarrow\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
\(\left|x\right|+3=5\)
Vì \(5>3\) nên \(\left|x\right|>0\)
\(x+3=5\)
\(x=5-3\)
\(x=2\)