a) \(\left(5^{2007}-5^{2006}\right)\div\left(5^{2005}.5\right)\)

\(=\left(5^{2007}-5^{2006}\right)\div5^{2006}\)

\(=5^{2007}\div5^{2006}-5^{2006}\div5^{2006}\)

\(=5-1=4\)

Giải:

Ta có:

\(\frac{3}{2\times5}+\frac{3}{5\times8}+\frac{3}{8\times11}+...+\frac{3}{\left(x-3\right)\times x}=\frac{1}{6}\)

\(\Leftrightarrow\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x-3}-\frac{1}{x}=\frac{1}{6}\)

\(\Leftrightarrow\frac{1}{2}-\frac{1}{x}=\frac{1}{6}\)

\(\Leftrightarrow\frac{1}{x}=\frac{1}{2}-\frac{1}{6}=\frac{1}{3}\Leftrightarrow x=3\)

De thoi ma,minh ko ghi lai de nha

=\(\frac{1}{2}\)-\(\frac{1}{5}\)+\(\frac{1}{5}\)-\(\frac{1}{8}\)+...+...=\(\frac{1}{6}\)

=\(\frac{1}{2}\)-\(\frac{1}{x}\)=\(\frac{1}{6}\)

Con lai bn tu lam nha . chuc bn hok tot !!!

55⁵ x 55¹⁰ = 55¹⁵

6666¹² x 6666¹⁰ = 6666²²

5¹⁰ x 5¹ = 5¹¹

22¹ x 22¹⁰ = 22¹¹

10¹ x 10² = 10¹²

55⁵x55¹⁰=55¹⁵

6666¹²x6666¹⁰=6666²²

5¹⁰x5¹=5¹¹

22¹x 22¹⁰=22¹¹

10¹x10²=10³

goi 3 so la a;b;c  theo de bai ta co  a+b=56    ;    b+c=64     ;     c+a=78

=> a+b+b+c+c+a=56+64+78=198      => a+b+c=99  (*)

thay a+b=56  vao * ta duoc   c=99-56=43

thay b+c=64   vao * ta duoc  a=99-64=35

thay c+a=78  vao * ta duoc    b=99-78=21

vay 3 so la 43;34;21

h dung nha

a) 71.2-6(2x+5)=10⁵:10³

<=>  71.2-6(2x+5)=10²

142-6(2x+5)=100

6(2x+5)=142-100

6(2x+5)=42

2x+5=7

2x=7-5

2x=2

x=2:2

x=1

địt mẹ mầy

a) Ta có:2^x + 2^y = 18

\(\Leftrightarrow\)2^x + 2^y = 2\(^1\)+2\(^4\)\(\Leftrightarrow\)x=1;y=4 và ngược lại.

b) Ta có:2^{x y} . 3^y = 12

\(\Leftrightarrow\)2^{x y} . 3^y = 2\(^2\).3\(^1\)

cai nay qua de