The concept of multiplication and division of rational numbers The absolute value of the multiplier is equal to the -?

The concept of multiplication and division of rational numbers The absolute value of the multiplier is equal to the -?

The absolute value of the multiplier is equal to the product of the absolute values of the multipliers

On the multiplication and division of rational numbers
1. Observe the following column: 1 / 2, 1 / 6, 1 / 12, 1 / 20 Please find out the rule of arrangement and fill in the blanks according to the rule________ The nth number______ .
2. Is the following calculation correct? If not, please write down the correct process
(- 30) × (half two thirds + four fifths) = - 30) × half two thirds + four fifths = - 15 two thirds + four fifths = - 14 and 15 13
3. In the first quarter of 2007, a company made an average monthly loss of 12000 yuan. In the second quarter, with the efforts of all employees, the company made an average monthly profit of 18000 yuan. In the third quarter, the company made an average monthly profit of 16000 yuan. In the fourth quarter, the company made a total loss of 28000 yuan. How about the company's overall profit in 2007?
4. Observe the following formulas: - 1 × 1 / 2 = - 1 + 1 / 2; - 1 / 2 × 1 / 3 = - 1 / 2 + 1 / 3; - 1 / 3 × 1 / 4 = - 1 / 3 + 1 / 4
(1) What's the rule you find___________ ；
(2) It is calculated by the law
(- 1 × 1 / 2) + (- 1 / 2 × 1 / 3) + (- 1 / 3 × 1 / 4) + +(- 1 / 2008 × 1 / 2009)

1.1/30,1/n*(n+1)
2.(-30)*(1/2-2/3+4/5)=-30*1/2+30*2/3-30*4/5=-15+20-24=-19
3.-1.2*4+1.8+1.6-2.8=-4.2
The loss was 42000 yuan
4.-1/n*1/(n+1)=-1/n+1/(n+1)
The original formula = - 1 + 1 / 2-1 / 2 + 1 / 3-1 / 3 + 1 / 4 -. + 1 / 2008-1 / 2008 + 1 / 2009
=-1+1/2009
=-2008/2009

What is the definition of rational number?

Integers and fractions are called rational numbers. Any rational number can be written as fraction M / N (m, n are integers, and N ≠ 0)
&The number of infinite acyclic decimals and open roots is called irrational number, such as π, 3.1415926535897932384626
&Rational numbers are just the opposite of rational numbers. Integers and fractions are called rational numbers