Question

Tính A= 1/(x+1)(x+2) + 1/(x+2)(x+3) + 2/(x+3)(x+4) + 4/ (x+4)(x+5) + 8/ (x+5)(x+6)

Answer 1

=\(\frac{1}{x+1}-\frac{1}{x+2}\)+\(\frac{1}{x+2}-\frac{1}{x+3}\)+\(\frac{1}{x+3}-\frac{1}{x+4}+\frac{1}{x+4}\)-\(\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+6}\)

=\(\frac{1}{x+1}-\frac{1}{x+6}\)

=\(\frac{x+6-x-1}{\left(x+1\right)\left(x+6\right)}\)

=\(\frac{5}{\left(x+1\right)\left(x+6\right)}\)

Answer 2

2/(x+3)(x+4) sao lại bằng 1/(x+3)(x+4) được bạn

Answer 3

a) 2/3 x 3/4 x 4/5 : 1/5
= 1/2 x 4
= 2
b) 1 x 2 x 3 x 4/5 x 6 x 7 x 8
= 2 x 3 x 24/5 x 56
= 6 x 72/5 x 56
= 432/5 x 56
= 24192/5
c) 2/5 x 3/4 x 5/6 : 3/4
= 3/10 x 10/9
= 1/3