không bt gì hết á

Do  a = b = 1  nên ta có thể đặt a = cos A + i sin A ; b = cos B + i sin B  

Khi đó ta có

x = cos A + cos B 2 + sin A + sin B + 1 2 y = cos A cos B - sin A sin B - sin A - sin B 2 + cos A sin B + sin A cos B + cos A + cos B 2  

Rút gọn ta có

x = 3 + 2 cos A - B + 2 sin A + sin B y = 3 + 2 cos A - B + 2 sin A + sin B  

Do đó x = y

Đáp án A

a)x=\(\frac{-22}{77}\);   y=\(\frac{-21}{77}\)

Vì -22< -21 nên \(\frac{-22}{77}< \frac{-21}{77}\)

Vậy \(\frac{2}{-7}< \frac{-3}{11}\)

b)x=\(\frac{-71}{100}\);    y=\(\frac{-72}{100}\)

Vì -71>-72 nên \(\frac{-71}{100}>\frac{-72}{100}\)

Vậy \(\frac{-213}{300}< \frac{18}{-25}\)

y = 0 , 75 = 3 4 = 15 20   n ê n   x > y

Câu 1: B

Câu 2: B

(Sửa \(cn-bm\rightarrow cn-dm\))

Ta có :

\(\left\{{}\begin{matrix}ad-bc=1\\cn-dm=1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}ad=1+bc\\cn=1+dm\end{matrix}\right.\)

\(\dfrac{x}{y}=\dfrac{a}{b}.\dfrac{d}{c}=\dfrac{ad}{bc}=\dfrac{1+bc}{bc}=1+\dfrac{1}{bc}>1\left(bc>0\right)\)

\(\Rightarrow x=\dfrac{a}{b}>y=\dfrac{c}{d}\left(2\right)\)

\(\dfrac{y}{z}=\dfrac{c}{d}.\dfrac{n}{m}=\dfrac{cn}{dm}=\dfrac{1+dm}{dm}=1+\dfrac{1}{dm}>1\left(dc>0\right)\)

\(\Rightarrow y=\dfrac{c}{d}>z=\dfrac{m}{n}\left(2\right)\)

\(\left(1\right);\left(2\right)\Rightarrow x>y>z\)

a, -213/300 = -71/100

18/-25 = -72/100

vì -71 > -72 

suy ra -71/100 > -72/100

suy ra x > y

b, -0,75 = -3/4

suy ra x = y