Mathematics problem of grade one in junior high school Calculation: - 1 / 10 × 11-1 / 11 × 12-1 / 12 × 13... - 1 / 19 × 20 =?

Mathematics problem of grade one in junior high school Calculation: - 1 / 10 × 11-1 / 11 × 12-1 / 12 × 13... - 1 / 19 × 20 =?

Put forward the minus sign first, and I will not talk about it later. I will add it after the calculation
If it's 1 / (10 * 11), it's a math problem in grade one or an intelligence problem in primary school
Change to (11-10) / (10 * 11), further disassemble: (1 / 10) - (1 / 11)
Take each one apart in this way. You can omit all the items in the middle, and then you can add the items at both ends
Add a minus sign to the end
If it's 1 / 10 * 11, that's 11 / 10, it's not interesting. Split it into 1 + 1 / 10, and each one will be split in this way,
Then add it up