Tính phí

How old is he ?

He is 40 years old

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Tính phí

2

\(A=2^1+2^2+2^3+...+2^{100}\)

\(2\text{A}=2^2+2^3+2^4+...+2^{101}\)

\(2\text{A}-A=\left(2^2+2^3+2^4+...+2^{101}\right)-\left(2^1+2^2+2^3+...+2^{100}\right)\)

\(A=2^{101}-2\)

Đặt \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\)=k

=>a=bk;c=dk

Ta có:

\(\dfrac{a+b}{a-b}\)=\(\dfrac{bk+b}{bk-b}\)=\(\dfrac{b\left(k+1\right)}{b\left(k-1\right)}\)=\(\dfrac{k+1}{k-1}\)(1)

\(\dfrac{c+d}{c-d}\)=\(\dfrac{dk+d}{dk-d}\)=\(\dfrac{d\left(k+1\right)}{d\left(k-1\right)}\)=\(\dfrac{k+1}{k-1}\)(2)

Từ (1) và (2) =>\(\dfrac{a+b}{a-b}\)=\(\dfrac{c+d}{c-d}\)

Vậy từ tỉ lệ thức\(\dfrac{a}{b}\)=\(\dfrac{c}{d}\)ta có thể suy ra tỉ lệ thức\(\dfrac{a+b}{a-b}\)=\(\dfrac{c+d}{c-d}\)(đpcm)

I enjoyed Big Heart 2 years ago

Because I wanted to help people in hospital

I have donate blood twice and given present to sick children

last month you left happy when you made a Mid-Autumn Festival lanter yourself and gave it to a little girl in hospital who loved it so much