Question

Rút gọn : B=(1-\(\frac{1}{2}\)) x ( 1-\(\frac{1}{3}\)) x ( 1-\(\frac{1}{4}\)) x ..... x (1 - \(\frac{1}{20}\))

m.n giúp mk nha mk cần gấp

Answer 1

\(B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}....\frac{19}{20}=\frac{1}{20}\)

Answer 2

\(B=\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{20}\right)\)

\(B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{19}{20}\)

\(B=\frac{1}{20}\)

Answer 3

B=(1-1/2)*(1-1/3)*.....*(1-1/20)

B=1/2*2*3*...*19/20

B=1/20

Answer 4

Bài này dễ mà ...

\(B=\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\cdot\cdot\left(1-\frac{1}{20}\right)\)

\(\Rightarrow B=\left(\frac{2}{2}-\frac{1}{2}\right)\cdot\left(\frac{3}{3}-\frac{1}{3}\right)\cdot\cdot\cdot\left(\frac{20}{20}-\frac{1}{20}\right)\)

\(\Rightarrow B=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\cdot\cdot\frac{18}{19}\cdot\frac{19}{20}=\frac{1\cdot2\cdot3\cdot\cdot\cdot18\cdot19}{2\cdot3\cdot4\cdot\cdot\cdot19\cdot20}\)

\(\Rightarrow B=\frac{1}{20}\)

Chúc bn học tốt !