A = − 9 . − 3 + 21. − 2 + 25 A = 27 + − 42 + 25 A = 27 + 25 + − 42 = 10 B = − 5 − 13 + − 3 . − 7 − 80 B = 65 + 21 − 80 B = 86 − 80 = 6

Vậy A > B

Thực hiện phép tính ta được A = l0 ; B = 6.

Từ đó suy ra A > B.

A = − 9 . − 3 + 21. − 2 + 25 A = 27 + − 42 + 25 A = 27 + 25 + − 42 = 10

B = − 5 − 13 + − 3 . − 7 − 80 B = 65 + 21 − 80 B = 86 − 80 = 6

Vậy A > B

Thực hiện phép tính ta được A = l0 ; B = 6.

Từ đó suy ra A > B.

\(B=\left(1-\frac{1}{4}\right)\left(1-\frac{1}{9}\right)...\left(1-\frac{1}{81}\right)\left(1-\frac{1}{100}\right)\)

\(B=\frac{3}{4}\cdot\frac{8}{9}\cdot...\cdot\frac{80}{81}\cdot\frac{99}{100}\)

\(B=\frac{1.3}{2.2}\cdot\frac{2.4}{3.3}\cdot...\cdot\frac{8.10}{9.9}\cdot\frac{9.11}{10.10}\)

\(B=\frac{\left(1\cdot2\cdot...\cdot8\cdot9\right).\left(3\cdot4\cdot...\cdot10\cdot11\right)}{\left(2\cdot3\cdot..\cdot9\cdot10\right).\left(2\cdot3\cdot...\cdot9\cdot10\right)}\)

\(B=\frac{1\cdot2\cdot...\cdot8\cdot9}{2\cdot3\cdot...\cdot9\cdot10}\cdot\frac{3\cdot4\cdot...\cdot10\cdot11}{2\cdot3\cdot...\cdot9\cdot10}\)

\(B=\frac{1}{10}\cdot\frac{11}{2}=\frac{11}{20}\)

Vì 20 < 21 nên 11/20 > 11/21

Vậy ..... 

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\(A=\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)...\left(1-\frac{1}{19}\right)\left(1-\frac{1}{20}\right)\)

\(A=\frac{1}{2}\cdot\frac{2}{3}\cdot...\cdot\frac{18}{19}\cdot\frac{19}{20}\)

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

Vì 20 < 21 nên 1/20 > 1/21 

Vậy ............

a: \(9^{20}=3^{40}>3^{39}=27^{13}\)

b: \(2^{21}=8^7< 9^7=3^{14}\)

\(a,\left(-12\right).1125.\left(-9\right).\left(-5\right).3=-1822500< 0\)

\(b,21.\left(-25\right).\left(-6\right).\left(-3\right).18.\left(-2022\right)=343942200>0\)