1,Tìm x ∈ để mỗi biểu thức là Phân số:

a,\(\dfrac{3}{x+5}\)

b ;\(\dfrac{x-1}{x-2}\)

2, Tìm x ∈ Z để mỗi biểu thức sau là giá trị nguyên:

a, \(\dfrac{7}{x-2}\)

b, \(\dfrac{x-5}{x-6}\)

c, \(\dfrac{2x+1}{x-2}\)

3, Tính:

a, 8\(\dfrac{1}{4}\) + 15\(\dfrac{1}{3}\)- 22\(\dfrac{1}{12}\)

b,\(\dfrac{2}{1.3}\)+ \(\dfrac{2}{3.5}\)+ \(\dfrac{2}{5.7}\)+........+ \(\dfrac{2}{99.100}\)

c, A= \(\dfrac{1}{2.4}\)+ \(\dfrac{1}{4.6}\)+ \(\dfrac{1}{6.8}\) +...............+ \(\dfrac{1}{100.102}\)