\(A=\frac{2006^{2006}+1}{2006^{2007}+1}\)                   VÀ    \(B=\frac{2006^{2005}+1}{2006^{2006}+1}\)

Ta có: \(A=\frac{2006^{2006}+1}{2006^{2007}+1}< 1\)

Nên \(A=\frac{2006^{2006}+1}{2006^{2007}+1}< \frac{2006^{2006}+1+2005}{2006^{2007}+1+2005}=\frac{2006^{2006}+2006}{2006^{2007}+2006}\)

                                                                                         \(=\frac{2006.\left(2006^{2005}+1\right)}{2006.\left(2006^{2006}+1\right)}\)

                                                                                            \(=\frac{2006^{2005}+1}{2006^{2006+1}}=B\)

Vậy \(A< B\)

⇔10A=102005+110(102004+1)​

⇒10�=102005+10102005+1⇒10A=102005+1102005+10​

10�=102005+1+9102005+1=102005+1102005+1+9102005+110A=102005+1102005+1+9​=102005+1102005+1​+102005+19​

10�=1+9102005+110A=1+102005+19​

tương tự như trên ta có :

10�=1+9102006+110B=1+102006+19​

ta thấy:102005+1<102006+1

⇒9102005+1>9102006+1⇒102005+19​>102006+19​

⇒1+9102005+1>1+9102006+1⇒1+102005+19​>1+102006+19​

=>10A>10B

=>A>B

a) \(13\times17-256:16+14:7-1\)

\(=221-16+2-1\)

\(=206\)

Huyền ơi cùng anh nào đấy kks

\(5x\cdot5x\cdot5x=\left(5x\right)^3\)

\(x^1\cdot x^2\cdot...\cdot x^{2006}=x^{2013021}\)

\(x\cdot x^4\cdot x^7\cdot...\cdot x^{100}=x^{1717}\)

\(x^2\cdot x^5\cdot x^8\cdot...\cdot x^{2003}=x^{669670}\)

Nếu đúng thì cho mình xin cái !!!

\(x^1\cdot x^2\cdot...\cdot x^{2006}=x^{\frac{\left(2006+1\right)2006}{2}}=x^{2013021}\)

\(x\cdot x^4\cdot x^7\cdot...\cdot x^{100}=x^{\frac{\left(100+1\right)\left(\frac{100-1}{3}+1\right)}{2}}=x^{1717}\)

\(x^2\cdot x^5\cdot x^8\cdot...\cdot x^{2003}=x^{\frac{\left(2003+2\right)\left(\frac{2003-2}{3}+1\right)}{2}}=x^{669670}\)

Hơi khó nhìn bn thông cảm!

Ai mà tính đc bạn

1-3=1(1-3)

3²-3³=3²(1-3)

Ta có :

\(x=2005\Rightarrow x+1=2006\)

Thay \(2006=x+1\) vào biểu thức trên ta được : 

\(x^{2005}-\left(x+1\right)x^{2004}+\left(x+1\right)x^{2003}-\left(x+1\right)x^{2002}+...-\left(x+1\right)x^2+\left(x+1\right)x-1\)

\(=x^{2005}-x^{2005}+x^{2004}-x^{2004}+x^{2003}-...-x^3+x^2-x^2+x-1\)

\(=x-1\) mà \(x=2005\)

\(\Rightarrow x^{2005}-2006.x^{2004}+2006.x^{2003}-2006.x^{2002}+...-2006.x^2+2006x-1=2005-1=2004\)

\(3^{2006}:3^{2005}+10^3:10^2\)

= \(3^{2006-2005}+10^{3-2}\)

= \(3^1+10^1\)

= 3 + 10

= 13
 

30 mu 1

3²⁰⁰⁶ : 3²⁰⁰⁵ + 10³ : 10² = 3 + 10 = 13
Tích mk nhé

1.

a) \(5x.5x.5x=\left(5x\right)^3.\)

b) \(x^1.x^2.....x^{2006}=x^{\frac{\left(2006+1\right).2006}{2}=}x^{2013021}.\)

c) \(x^1.x^4.x^7.....x^{100}=x^{\frac{\left(100+1\right).\left(\frac{100-1}{3}+1\right)}{2}}=x^{1717}.\)

d) \(x^2.x^5.x^8.....x^{2003}=x^{\frac{\left(2003+2\right).\left(\frac{2003-2}{3}+1\right)}{2}}=x^{669670}.\)

2.

\(2^x+80=3^y\)

Với \(x>0\Rightarrow2^x\) chẵn

Và 80 chẵn

\(\Rightarrow2^x+80\) chẵn.

Mà \(3^y\) lẻ

\(\Rightarrow x< 0.\)

Mà \(x\in N\)

\(\Rightarrow x=0.\)

\(\Rightarrow2^0+80=3^y\)

\(\Rightarrow1+80=3^y\)

\(\Rightarrow3^y=81\)

\(\Rightarrow3^y=3^4\)

\(\Rightarrow y=4.\)

Vậy \(\left(x;y\right)=\left(0;4\right).\)

Chúc bạn học tốt!

1.viết tích dưới dạng lũy thừa

a.5x.5x.5x

=(5x)\(^3\)

b.x\(^1\) . x \(^2\).......x \(^{2006}\)

=x \(^{2013021}\)

c.x\(^1\).x \(^4\) .x \(^7\)......x \(^{100}\)

=x \(^{1717}\)

d.x \(^2\) .x \(^5\).x \(^8\).......x\(^{2003}\)

=x \(^{669670}\)

2 \(^x\)+80=3\(^y\)

ta có 3\(^y\)lẻ nên 2 \(^x\)+80 lẻ .

Với x \(\ge\)1

thì 2 \(^x\)+80 chẵn không thỏa mãn

nên x=0

=>1+80=3\(^y\)

=>81=3\(^y\)

=>3\(^4\)=3\(^y\)

=>y=4