Question

1)\(\dfrac{2^{18}}{32^3}.\dfrac{27^4}{54^3}\)	4)\((\dfrac{1}{2})^x=\dfrac{1}{32}\)
2)\(\dfrac{40^4}{120^4}.\dfrac{130^3}{390^3}\)	5)\(\dfrac{x+1}{9}=\dfrac{4}{x+1}\)
3)\(2^x=8\)	6)\(\dfrac{2x}{5}=\dfrac{10}{x}\)

	7)\(19.5^{2x+7}=475\)
	8)\(33^x:11^x=243\)
	9)Tìm x, y biết: 5x=4y và y-x=7

Answer 1

9) Theo bài, ta có : 5x = 4y

\(\Rightarrow\dfrac{x}{4}=\dfrac{y}{5}\)

Mà y - x = 7

Theo tính chất dãy tỉ số bằng nhau, ta có :

\(\dfrac{x}{4}=\dfrac{y}{5}=\dfrac{y-x}{5-4}=\dfrac{7}{1}=7\)

Do đó : \(\dfrac{x}{4}=7\Rightarrow x=7.4=28\)

\(\dfrac{y}{5}=7\Rightarrow y=7.5=35\)

Vậy x = 28 ; y = 35

Answer 2

4) \(\left(\dfrac{1}{2}\right)^x\) = \(\dfrac{1}{32}\)

\(\left(\dfrac{1}{2}\right)^x\)\(=\left(\dfrac{1}{2}\right)^5\)

\(\Rightarrow x=5\)

Vậy x = 5

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Answer 3

3) \(2^x\) = 8

\(2^x\) = \(2^3\)

\(\Rightarrow x=3\)

Vậy x = 3

Answer 4

1: \(=\dfrac{2^{18}}{2^{15}}\cdot\dfrac{3^{12}}{3^9\cdot2^3}=3^3=27\)

4: =>(1/2)^x=(1/2)^5

=>x=5

7: =>5^2x+7=25

=>2x+7=2

=>2x=-5

=>x=-5/2

8: =>3^x=243

=>x=5