Trả lời :

Phép so sánh C đúng nhoa bn =))

~ Thiên Mã ~

Đáp án đúng là câu C

gọi đò sang

học tốt nha

bn

hello hãy thử ném 12 gánh cam qua sông rồi hãy trả lời câu hỏi

bằng 2000

Trả lời :

1000 + 1000

= 2000

Oki bn !!

~ Thiên Mã ~

\(S=\frac{5}{2^2}+\frac{5}{3^2}+\frac{5}{4^2}+...+\frac{5}{100^2}\)

\(\Rightarrow S=5\left(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{100^2}\right)\)

\(\Rightarrow S< 5\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)

\(\Rightarrow S< 5\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(\Rightarrow S< 5\left(1-\frac{1}{100}\right)< 5.1=5\)

Vậy S < 5 (đpcm)

\(S=\frac{5}{2^2}+\frac{5}{3^2}+\frac{5}{4^2}+...+\frac{5}{100^2}\)

\(\Rightarrow S=5\left(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{100^2}\right)\)

\(\Rightarrow S>5\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{100.101}\right)\)

\(\Rightarrow S>5\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{100}-\frac{1}{101}\right)\)

\(\Rightarrow S>5\left(\frac{1}{2}-\frac{1}{101}\right)\)

\(\Rightarrow S>5\left(\frac{101}{202}-\frac{2}{202}\right)\)

\(\Rightarrow S>5.\frac{99}{202}=\frac{495}{202}>2\)

Vậy S > 2 ( đpcm)

\(\left(\frac{4}{5}-\frac{1}{2}x\right)^2=\frac{1}{4}\)

\(\Leftrightarrow\orbr{\begin{cases}\frac{4}{5}-\frac{1}{2}x=\frac{1}{2}\\\frac{4}{5}-\frac{1}{2}x=\frac{-1}{2}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{3}{5}\\x=\frac{13}{5}\end{cases}}}\)

Vậy \(x\in\left\{\frac{3}{5};\frac{13}{5}\right\}\)

\(\left(\frac{4}{5}-\frac{1}{2}x\right)^2=\frac{1}{4}\)

\(\Leftrightarrow\orbr{\begin{cases}1-\frac{1}{2}x=\sqrt{\frac{1}{4}}\\1-\frac{1}{2}x=-\sqrt{\frac{1}{4}}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x-\frac{1}{2}x=\frac{1}{2}\\x-\frac{1}{2}x=-\frac{1}{4}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\x=3\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\x=3\end{cases}}\)

Không hiểu phần nào thì hỏi