Question

1: Tìm x biết :

a, x + 3/22=27/121.11/9

b, 1-x=49/65.5/7

c, 5/11.16/10-(x+1/3)=5/22

d, -13/11.22/26-x mũ 2 = 7/16

2: tinh :

a, 2/3:(3/5+3/7)

b, (5/9-7/3):-5/3

3: Tính : B=1/3+ 1/3 mu 2+ 1/3 mu 3 +............+ 1/3 mu 101

4: a ,Chứng tỏ rằng:

2/n(n+1)(n+2) = 1/n(n+1)-1/(n+1)(n+2)

b, Áp dụng tính :

1/1.2.3+1/2.3.4+1/3.4.5+...+1/98.99.100

Answer 1

1)

a)\(x+\dfrac{3}{22}=\dfrac{27}{121}.\dfrac{11}{9}\)

\(x+\dfrac{3}{22}=\dfrac{3}{11}\)

\(x=\dfrac{6}{22}-\dfrac{3}{22}\)

\(x=\dfrac{3}{22}\)