Question

A= (1-1/4) x (1-1/9) x (1-1/16) x .... x (1-1/121)
1/4 là một phần bốn 1/9 cũng thế

Answer 1

giúp mik với ạ

Answer 2

ta có :

A=$\left(-\frac{3}{4}\right)\left(-\frac{8}{9}\right)\left(-\frac{15}{16}\right)...\left(-\frac{120}{121}\right)$(có 10 số hạng)

  = $\frac{3\cdot 8\cdot 15\cdot ...\cdot 120}{4\cdot 9\cdot 16\cdot ...\cdot 121}=\frac{\left(1.3\right)\left(2\cdot 4\right)\left(3\cdot 5\right)\cdot ...\cdot \left(10\cdot 12\right)}{{}^{}\cdot {}^{}\cdot {}^{}\cdot ...\cdot {}^{}}=\frac{\left(1\cdot 2\cdot 3\cdot ...\cdot 10\right)\left(3\cdot 4\cdot 5\cdot ...\cdot 12\right)}{\left(2\cdot 3\cdot 4\cdot ..\cdot 11\right)\left(2\cdot 3\cdot 4\cdot ..\cdot 11\right)}$

=$\frac{12}{11\cdot 2}=\frac{12}{22}$

Answer 3

= 1222