a) 2/8 = 1/4

b) 6/18 = 1/3

C) 17/24 - 8/24 = 9/24 = 3/8

`#3107.101107`

`A = 1+ 3 + 3^2+3^3+…+3^101?`

`= (1 + 3 + 3^2) + (3^3 + 3^4 + 3^5) + ... + (3^99 + 3^100 + 3^101)`

`= (1 + 3 + 3^2) + 3^3 * (1 + 3 + 3^2) + ... + 3^99 * (1 + 3 + 3^2)`

`= (1 + 3 + 3^2) * (1 + 3^3 + ... + 3^99)`

`= 13 * (1 + 3^3 + ... + 3^99)`

Vì `13 * (1 + 3^3 + ... + 3^99) \vdots 13`

`=> A \vdots 13`

Vậy, `A \vdots 13.`

Yêu cầu là gì ạ?

\(a,=-x^3+3x^2+2x-6\)

\(\left(x^2-2\right)\left(-x+3\right)\)

\(=-x^3+3x^2+2x-6\)

\(A=\dfrac{\sqrt{3}\left(\sqrt{3}-1\right)}{\sqrt{3}-1}=\sqrt{3}\)

a: \(\sqrt{15-6\sqrt{6}}+\sqrt{33-12\sqrt{6}}\)

\(=\sqrt{9-2\cdot3\cdot\sqrt{6}+6}+\sqrt{24-2\cdot2\sqrt{6}\cdot3+9}\)

\(=\sqrt{\left(3-\sqrt{6}\right)^2}+\sqrt{\left(2\sqrt{6}-3\right)^2}\)

\(=3-\sqrt{6}+2\sqrt{6}-3=\sqrt{6}\)

b: \(\sqrt{\left(3+\sqrt{5}\right)^2}+\sqrt{14-6\sqrt{5}}\)

\(=\sqrt{\left(3+\sqrt{5}\right)^2}+\sqrt{\left(3-\sqrt{5}\right)^2}\)

\(=\left|3+\sqrt{5}\right|+\left|3-\sqrt{5}\right|\)

\(=3+\sqrt{5}+3-\sqrt{5}=6\)

c: \(\dfrac{3}{2\sqrt{3}+3}+\dfrac{3}{2\sqrt{3}-3}\)

\(=\dfrac{3\left(2\sqrt{3}-3\right)+3\left(2\sqrt{3}+3\right)}{12-9}\)

\(=2\sqrt{3}-3+2\sqrt{3}+3=4\sqrt{3}\)

d: \(\sqrt{\left(\sqrt{3}+4\right)\cdot\sqrt{19-8\sqrt{3}}+3}\)

\(=\sqrt{\left(4+\sqrt{3}\right)\cdot\sqrt{\left(4-\sqrt{3}\right)^2}+3}\)

\(=\sqrt{\left(4+\sqrt{3}\right)\cdot\left(4-\sqrt{3}\right)+3}\)

\(=\sqrt{16-3+3}=\sqrt{16}=4\)

e: \(\dfrac{9-2\sqrt{3}}{3\sqrt{6}-2\sqrt{2}}+\dfrac{3}{3+\sqrt{6}}\)

\(=\dfrac{\sqrt{3}\left(3\sqrt{3}-2\right)}{\sqrt{2}\left(3\sqrt{3}-2\right)}+\dfrac{3\left(3-\sqrt{6}\right)}{3}\)

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

  A = 1 +  3  + 3² + 3³ + ... + 3¹⁰⁰

3A = 3 + 3² + 3³ +3⁴+ .... + 3¹⁰¹

3A - A = (3 + 3² + 3⁴ + ... + 3¹⁰¹) - (1 + 3 + 3² + 3³ + ... + 3¹⁰⁰)

2A     = 3 + 3² + 3⁴ + ... + 3¹⁰¹ - 1 - 3 - 3² - 3³ - ... - 3¹⁰⁰

2A = (3 - 3) + (3² - 3²) + ... + (3¹⁰⁰ - 3¹⁰⁰) + (3¹⁰¹ - 1)

2A = 3¹⁰¹ - 1

A = \(\dfrac{3^{101}-1}{2}\)

Bài 1 : 

\(a.\sqrt{x^2-1}\)

\(ĐK:\)

\(x^2-1\ge0\)

\(\Leftrightarrow x^2\ge1\)

\(\Leftrightarrow\left[{}\begin{matrix}x\le-1\\x\ge1\end{matrix}\right.\)

Bài 2 : 

\(2\cdot\sqrt{\left(\sqrt{2}-3\right)^2}+\sqrt{48}-5\sqrt{50}\)

\(=2\cdot\left|\sqrt{2}-3\right|+4\sqrt{3}-25\sqrt{2}\)

\(=-2\cdot\left(\sqrt{2}-3\right)+4\sqrt{3}-25\sqrt{2}\)

\(=-2\sqrt{2}-6+4\sqrt{3}-25\sqrt{2}\)

\(=-27\sqrt{2}-6+4\sqrt{3}\)

\(A=\sqrt{3+\sqrt{5-\sqrt{\left(2\sqrt{3}+1\right)^2}}}=\sqrt{3+\sqrt{5-\left(2\sqrt{3}+1\right)}}\)

\(=\sqrt{3+\sqrt{4-2\sqrt{3}}}=\sqrt{3+\sqrt{\left(\sqrt{3}-1\right)^2}}\)

\(=\sqrt{3+\sqrt{3}-1}=\sqrt{2+\sqrt{3}}=\dfrac{1}{\sqrt{2}}\sqrt{4+2\sqrt{3}}\)

\(=\dfrac{1}{\sqrt{2}}\sqrt{\left(\sqrt{3}+1\right)^2}=\dfrac{\sqrt{3}+1}{\sqrt{2}}=\dfrac{\sqrt{2}+\sqrt{6}}{2}\)

\(A=\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}\\ =\sqrt{3+\sqrt{5-\sqrt{\left(1+2\sqrt{3}\right)^2}}}\\ =\sqrt{3+\sqrt{5-1+2\sqrt{3}}}\\ =\sqrt{3+\sqrt{\left(\sqrt{3}-1\right)^2}}\\ =\sqrt{3+\sqrt{3}-1}\\ =\sqrt{2+\sqrt{3}}\)

Ta có: \(A=\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}\)

\(=\sqrt{3+\sqrt{4-2\sqrt{3}}}\)

\(=\sqrt{3+\sqrt{3}-1}\)

\(=\sqrt{2-\sqrt{3}}\)

\(=\dfrac{\sqrt{4-2\sqrt{3}}}{\sqrt{2}}\)

\(=\dfrac{\sqrt{6}-\sqrt{2}}{2}\)