Khó quá

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

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

= 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 - 1/128 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128  ( Rồi giản ước )

= 1

#)Giải :

\(\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}+\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+...+\frac{1}{256}-\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{512}\)

\(=\frac{255}{512}\)

Lời giải 

\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+...+\frac{1}{256}-\frac{1}{512}\)

\(=\frac{1}{2}-\frac{1}{512}\)

\(=\frac{255}{512}\)

ai làm đc mà đúng mk tích cho

\(\left(190-2.x\right):35+32=16\)

\(=>\left(190-2x\right):35=-16\)

\(=>190-2x=-560\)

\(=>2x=750\)

\(=>x=375\)

Ủng hộ nha các bạn

(190 - 2 x X):35+32 = 16

(190 - 2 x X): 35 = 16 -32 = -16

(190 - 2 x X = (-16) x 35 = -560

2 x X = 190 - (-560)

2 x X = 190 + 560 = 750

X  =  750  :  2  =  350 

(190 - 2 x X) : 35 + 32 = 16

(190 - 2x) : 35 = 16 - 32

(190 - 2x) : 35 = -16

190 - 2x = -16 x 35

190 - 2x = -560

-2x = -560 - 190

-2x = -750

\(x=\frac{-750}{-2}=375\)

Đặt A = 1 + 2 + 4 + 8 + ..... + 1024

=> 2A = 2 + 4 + 8 + ..... + 2048

=> 2A - A = 2048 - 1

=> A = 2047

Đặt A = 1 + 2 + 4 + 8 + ... + 1024

=> 2A = 2 + 4 + 8 + ... + 2048

=> 2A - A = 2048 - 1

=> 2A = 2047

Đặt A =1+2+4+8+16+32+.....+1024

2A=2x(1+2+4+8+16+32+............+1024)

2A=2+4+8+......+2048

2A-A=(2+4+8+............+2048)-(1+2+4+............+1024)

A=2048 - 1

A=2047

đặt \(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+...+\frac{1}{256}\)

=> A=\(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}+....+\frac{1}{2^8}\)

=> 2A=\(1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+....+\frac{1}{2^7}\)

=> 2A-A=\(\left(1+\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+....+\frac{1}{2^7}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+....+\frac{1}{2^8}\right)\)

=> A=\(1-\frac{1}{2^8}\)

(1+2+3+4+....+1000)x(512-512)

=(1+2+3+4+....+1000)X0=0

thanks bn nha mờ chỉ viết vậy thui àk Nguyễn Tiến Dũng

b: A=1/3+1/9+...+1/3^10

=>3A=1+1/3+...+1/3^9

=>A*2=1-1/3^10=(3^10-1)/3^10

=>A=(3^10-1)/(2*3^10)

c: C=3/2+3/8+3/32+3/128+3/512

=>4C=6+3/2+...+3/128

=>3C=6-3/512

=>C=1023/512

d: A=1/2+...+1/256

=>2A=1+1/2+...+1/128

=>A=1-1/256=255/256

a)524.[23+(-45)] + 524.(-45+123)

=524.(-22) + 524.78

=524.(-22+78)

=524.100

=52400