Tính nhanh:\(\frac{11}{3}x\frac{26}{7}-\frac{26}{7}x\frac{8}{3}\)
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1. the earthquake./damaged/Almost/was/all of my house/by/
--> Almost all of my house was damaged by the earthquake.
2. disasters./More trees/should be/to prevent/some natural/planted/
--> More trees should be planted to prevent some natural disaster.
3. to hurricanes./to give names/The people/are/the first/in Puerto Rico/
--> The people are the first in Puerto Rico to give names to hurricane
4. rained/Though/went/we/it/heavily/school/to/time/on.
--> Though it rained heavily we went to school on time
Ta có F(0)=c=0
=>c=0
Ta lại có F(1)=a×1^2+b×1+c=2
F(1)=a+b+0=2
F(1)=a+b=2
Ta lại có F(2)=a×2^2+2b+c=2
F(2)=4a+2b+0=2
F(2)=4a+2b=2
F(2)=2a+b=1
F(2)=2a+b-2=1-2=-1
F(2)=2a+b-a-b=-1 (Do a+b=1)
F(2)=a=-1
Thay a=-1 vào a+b=1
Ta có -1+b=1
=>b=2
Vậy a=-1,b=2
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\)
\(=1-\frac{1}{100}=\frac{99}{100}\)