Núi Thái Sơn

gọi tổng đó là A ta có :

A = 1/2 + 1/4 + 1/8 +1/16 + 1/32 +1/64 + 1/128

2A= ( 1/2 * 2) + ( 1/4 * 2 ) + ( 1/8 * 2) + ( 1/16 * 2) + ( 1/32 * 2 ) + ( 1/64 * 2 ) + ( 1/128 * 2)

2A= 1+ 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64

TA LẤY 2A - 1A =  1A

A = ( 1 + 1/2 +1/4 + 1/8 + 1/16 + 1/32 + 1/64 ) -  ( 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 )

TA THẤY 1/2 - 1/2 = 0 ; 1/4 - 1/4 = 0 ; 1/8 - 1/8 = 0 ;1/16 - 1/16 = 0 ; 1/32 - 1/32 = 0 ; 1/64- 1/64 = 0 

NÊN A = 1 - 1/128 = 127/128

27;28;29

= (x+2)(3-4x+x+2)=0 => x=2;-5/3

A

\(536.60+536.39+536=536\left(60+39+1\right)=536.100=53600\)

2+3x4=14                    

hù

hù hù hù

Khó ghêKhó ghêKhó ghêKhó ghêKhó ghêKhó ghêKhó ghê

= ( 1/2 + 3/4 + 4/5 ) : 3

= 41/20 :  3

= 41/60