Qua C vẽ tia Cz // DE

⇒ ∠DCz = ∠CDE = 108⁰

⇒ ∠zCA = ∠DCz - ∠DCA

= 108⁰ - 48⁰

= 60⁰

⇒ ∠zCA = ∠CAB = 60⁰

Mà ∠zCA và ∠CAB là hai góc so le trong

⇒ Cz // AB

Lại có:

Cz // DE

⇒ AB // DE

\(\dfrac{-3}{4}< \dfrac{a}{12}< \dfrac{-5}{9}\)

\(\Rightarrow\dfrac{-27}{36}< \dfrac{3a}{36}< \dfrac{-20}{36}\)

\(\Rightarrow-27< 3a< -20\)

\(\Rightarrow a=\left\{-8;-7\right\}\)

\(\dfrac{1}{1-\dfrac{1}{1-2^{-1}}}+\dfrac{1}{1+\dfrac{1}{2^{-1}}}\)

\(=\dfrac{1+\dfrac{1}{2^{-1}}+1-\dfrac{1}{2^{-1}}}{\left(1-\dfrac{1}{2^{-1}}\right)\left(1+\dfrac{1}{2^{-1}}\right)}\)

\(=\dfrac{2}{\left(1-2\right)\left(1+2\right)}=\dfrac{2}{1-4}=-\dfrac{2}{3}\)

J z bạn

mũ 2

0,(6) mux bằng 0,(6)^x

chắc là quan điểm đồng tình ý bn =))

On time: đúng lúc theo một lịch trình có sẵn, kế hoạch 

In time: không có kế hoạch, lịch trình( kịp lúc để làm một hoạt động khác) 

VD1 : Even though it rained, I still went to school on time 

VD2: The test will start in 5 minutes. I hope he can arrive here in time 

On time:dung luc,dung thoi diem va thoi gian da len ke hoach truoc do

In time:khong co lich trinh hoac ke hoach truoc do,vua kip luc de lam mot dieu gi do

Vd on time:She is a hard-working student,he is always goes to school on time

Vd in time:He rushed to catch the train and arrived at the station just in time for the departure

\(6\left(x-\dfrac{1}{4}\right)=4\left(\dfrac{5}{6}+x\right)\)

\(6x-\dfrac{3}{2}=\dfrac{10}{3}+4x\)

\(2x=\dfrac{10}{3}+\dfrac{3}{2}=\dfrac{29}{6}\)

\(x=\dfrac{29}{12}\)

6.x-3/2=4.x+10/3

6.x-3/2+3/2=4.x+10/3+3/2

6.x=4.x+29/6

6.x-4.x=4.x+29/6-4.x

2.x=29/6

x=29/12