nếu a>0 ;b<0

\(\Rightarrow\left\{{}\begin{matrix}3a^2b^{1004}>0\\-19a^5b^{1008}< 0\end{matrix}\right.\)(ko thỏa mãn đề bài)

nếu a<0;b>0

\(\Rightarrow\left\{{}\begin{matrix}3a^2b^{1004}>0\\-19a^5b^{1008}>0\end{matrix}\right.\)(thỏa mãn)

vậy a là dấu âm,b là dấu dương

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.

“Why are you so mad?” “You _________me you weren’t coming to dinner. I waited for you for two hours.”

A. should tell

B. should have told 

C. should told

D. should had told

Mark the letter A, B, C or B on your answer sheet to indicate the correct answer to each of the following questions.

Biologists have introduced a global list of endangered and vulnerable animal species.

A. rare and specious

B. small but invaluable

C. weak and easily hurt 

D. strong and unusual

4S=\(\dfrac{4}{2^2}-\dfrac{4}{2^4}+\dfrac{4}{2^6}-...+\dfrac{4}{2^{4n-2}}-\dfrac{4}{2^{4n}}+...+\dfrac{4}{2^{2002}}-\dfrac{4}{2^{2004}}\)

4S=1-\(\dfrac{1}{2^2}+\dfrac{1}{2^4}-,...-\dfrac{1}{2^{2002}}\)

4S+S=1-\(\dfrac{1}{2^{2004}}\)

5S=\(\dfrac{2^{2004}-1}{2^{2004}}\)<1

\(\Rightarrow\)5S<1 hay S<\(\dfrac{1}{5}\)=0,2(đpcm)