Ta có :

A = \(\dfrac{20\cdot\left(20^{18}+1\right)}{20^{19}+1}=\dfrac{20^{19}+20}{20^{19}+1}=\dfrac{\left(20^{19}+1\right)-20}{20^{19}+1}=1-\dfrac{1}{20^{19}+1}\)B = \(\dfrac{20\cdot\left(20^{17}+1\right)}{20^{18}+1}=\dfrac{20^{18}+20}{20^{18}+1}=\dfrac{\left(20^{18}+1.\right)-20}{20^{18}+1}=1-\dfrac{20}{20^{18}+1}\)

Do nên

ok

mai được ko

I) The boy is crying......in his room.

A) noisy B) noisily C) slow D) light

He is good singer. ( rewrite this sentence, using adverd)
He .. .................

My father is forty years old.

In the spring, the weather is always warm.

Ba plays table tennis everyday.

\(\dfrac{-4}{11}\cdot\dfrac{2}{5}+\dfrac{6}{11}\cdot\dfrac{-3}{11}\)

\(=\dfrac{-8}{55}+\dfrac{-18}{121}\)

\(=\dfrac{-2}{605}\)

R = \(\left(\dfrac{1}{2}+1\right)\cdot\left(\dfrac{1}{3}+1\right)\cdot....\cdot\left(\dfrac{1}{99}+1\right)\)

R = \(\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot....\cdot\dfrac{100}{99}\)

R = \(\dfrac{3\cdot4\cdot...\cdot100}{2\cdot3\cdot...\cdot99}\)

R = 50