2A = 1 + \(\dfrac{1}{2}\)+\(\dfrac{1}{2^2}\)+\(\dfrac{1}{2^3}\)+...+\(\dfrac{1}{2^{99}}\)

2A - A= 1- \(\dfrac{1}{2^{100}}\)

A= 1 

Gọi biểu thức trên là Acó:

A=1+1/2+1/2^2+1/2^3+...+1/2^99+1/2^100

2A=1/2+1/2^2+1/2^3+....+1/2^99+1/2^100+1/2^101

2A-A=(1/2+1/2^2+1/2^3+....+1/2^99+1/2^100+1/2^101)-(1+1/2+1/2^2+1/2^3+...+1/2^99+1/2^100)

A=1/2^101-1

A=-1

a) \(2^x=8\)

⇔ \(2^x=2^3\)

⇒ \(x=3\)

b) \(3^x=27\)

⇔ \(3^x=3^3\)

⇒ \(x=3\)

c) \(\left(-\dfrac{1}{2}\right)x=\left(-\dfrac{1}{2}\right)^4\)

⇔ \(x=\left(-\dfrac{1}{2}\right)^4\div\left(-\dfrac{1}{2}\right)\)

⇔ \(x=\left(-\dfrac{1}{2}\right)^3\)

d) \(x\div\left(-\dfrac{3}{4}\right)=\left(-\dfrac{3}{4}\right)^2\)

⇔ \(x=\left(-\dfrac{3}{4}\right)^2\cdot\left(-\dfrac{3}{4}\right)\)

⇔ \(x=\left(-\dfrac{3}{4}\right)^3=-\dfrac{27}{64}\)

d) \(\left(x+1\right)^3=-125\)

⇔ \(\left(x+1\right)^3=\left(-5\right)^3\)

⇔ \(x+1=-5\)

⇔ \(x=-5-1=-6\)

2:

a: (x-1,2)^2=4

=>x-1,2=2 hoặc x-1,2=-2

=>x=3,2(loại) hoặc x=-0,8(loại)

b: (x-1,5)^2=9

=>x-1,5=3 hoặc x-1,5=-3

=>x=-1,5(loại) hoặc x=4,5(loại)

c: (x-2)^3=64

=>(x-2)^3=4^3

=>x-2=4

=>x=6(nhận)

 BÚ

`1/2+2 1/4x-2/3=(3/2:5/4-1/2)`

`=>9/4x-1/6=6/5-6/5=0`

`=>9/4x=1/6`

`=>x=2/27`

Vậy...

1,7 bạn nhé 

Cám ơn 

1/2+1,2=

1/2=0,5

0,5+1,2=1,7

tk nha bạn

thank you bạn

(^_^)

bằng 1,7 nha bạn nếu là phân số thì là 17/10

\(=\left[\dfrac{1}{4}-\dfrac{6}{5}\right]-\dfrac{4}{5}+\dfrac{3}{4}\)

\(=\dfrac{1}{4}-\dfrac{6}{5}-\dfrac{4}{5}+\dfrac{3}{4}\)

=1/4+3/4-6/5-4/5

=1-2

=-1

\(\left[\left(\dfrac{-1}{2}\right)^2-1,2\right]-\left(0,8-\dfrac{3}{4}\right)\)

\(=\left[\dfrac{1}{4}-\dfrac{6}{5}\right]-\left(\dfrac{4}{5}-\dfrac{3}{4}\right)\)

\(=\dfrac{1}{4}-\dfrac{6}{5}-\dfrac{4}{5}+\dfrac{3}{4}\)

\(=\left(\dfrac{1}{4}+\dfrac{3}{4}\right)-\left(\dfrac{6}{5}+\dfrac{4}{5}\right)\)

\(=1-2\)

\(=-1\)

bai tap nay lop may day

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