1.

a//b mà b⊥CD nên a⊥CD 

Do đó \(\widehat{D}=90^0\)

Góc A là góc nào??

2.

a, Vì a và b cùng vuông góc với MN nên a//b

b, a//b \(\Rightarrow\widehat{P}+\widehat{Q}=180^0\left(trong.cùng.phía\right)\Rightarrow\widehat{P}=70^0\)

5 + 9/14 = 70/14 + 9/14 = 79/14
6/54 : 8 = 6/54 x 1/8 = 1/72
5 - 13/17 = 85/17 - 13/17 = 72/17
3 : 9/10 = 3/1 x 10/9 = 10/3
24/72 - 202/909 = 1/9
9/11 : 5/13 = 9/11 x 13/5 = 117/55

\(5 +\) \(\dfrac{9}{14}\) = \(\dfrac{70}{14}\) + \(\dfrac{9}{14}\) = \(\dfrac{79}{14}\)
\(\dfrac{6}{54}\) \(: 8 =\) \(\dfrac{1}{9}\) \(:\) \(\dfrac{8}{1}\) = \(\dfrac{1}{9}\) x \(\dfrac{1}{8}\) = \(\dfrac{1}{72}\)
\(5 -\) \(\dfrac{13}{17}\) = \(\dfrac{85}{17}\) \(-\) \(\dfrac{13}{17}\) = \(\dfrac{72}{17}\)
\(3\) \(:\) \(\dfrac{9}{10}\) = \(\dfrac{3}{1}\) \(: \) \(\dfrac{9}{10}\) = \(\dfrac{3}{1}\) x \(\)\(\dfrac{10}{9}\) = \(\dfrac{30}{9}\) = \(\dfrac{10}{3}\)
\(\dfrac{24}{72}\) - \(\dfrac{202}{909}\) = \(\dfrac{3}{9}\) - \(\dfrac{2}{9}\) = \(\dfrac{1}{9}\)
\(\dfrac{9}{11}\) : \(\dfrac{5}{13}\) = \(\dfrac{9}{11}\) x \(\dfrac{13}{5}\) = \(\dfrac{117}{55}\)

 

a) \(2^4+8\left[\left(-2\right)^2:\dfrac{1}{2}\right]^0-2^{-2}.4+\left(-2\right)^2\)

\(=2^4+8.1-\dfrac{1}{4}.4+4\)

\(=16+8-1+4\)

\(=24-1+4\)

\(=23+4\)

\(=27\)

Bài 4: 
\(8^{12}\)\(-2^{33}\)-\(2^{30}\) chia hết cho 55
= \(2^{36}\)-\(2^{33}\)-\(2^{30}\)
= \(2^{30}.\left(2^6-2^3-1\right)\)
= \(2^{30}\). 55 chia hết cho 55 (đpcm)

Bài 3:
Ta có: \(5^{1000}=\left(5^2\right)^{500}=25^{500}\)
\(3^{1500}=\left(3^3\right)^{500}=27^{500}\)
Do \(25^{500}< 27^{500}\Rightarrow5^{1000}< 3^{1500}\)

Bài 3: 

Ta có: a//b

nên \(x+y=180\)

mà \(2x-3y=0\)

nên \(\left\{{}\begin{matrix}x+y=180\\2x-3y=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+2y=180\\2x-3y=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}5y=180\\x+y=180\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=36\\x=144\end{matrix}\right.\)

10 + 20 + 10 + 90

= ( 10 + 20 ) + ( 10 + 90 ) 

=        30      +        100

=                 130 

HỌC TỐT

10 + 20 + 10 + 90

= ( 10 + 20 ) + ( 10 + 90 )

= 30 + 100

= 130

10 + 20 + 10 + 90

= [ 10+ 20 ] + [10 + 90 ]

=     30        +     100

=             130

\(x\left(x-\frac{1}{3}\right)< 0\)

Để \(x\left(x-\frac{1}{3}\right)< 0\)thì x và \(x-\frac{1}{3}\)trái dấu nhau

Thấy \(x>x-\frac{1}{3}\)\(\Rightarrow\hept{\begin{cases}x>0\\x-\frac{1}{3}< 0\end{cases}\Rightarrow\hept{\begin{cases}x>0\\x< \frac{1}{3}\end{cases}\Leftrightarrow}0< x< \frac{1}{3}}\)

https://hoc24.vn/cau-hoi/.7405828739440

1 Lan goes to the supermarket on foot

2 Our garden has many flowers

3 He has black hair

4 We don't have to finish the task today (not necessary => don't have to: không cần làm gì, còn must not là không được làm gì nên câu này đề cho must là sai)

5 Are there 23 students in your class?

6 Lan is not as young as Minh