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7 tháng 8 2021

1 I said my car had been stolen a few weeks before

2 He said his boss had arrived late the night before

3 We say we had to go there then

4 She said she would go to her village the next week

5 I asked him if I could drive his car

8 tháng 8 2021

ta có sinB=\(\dfrac{AH}{AB}\)\(\Rightarrow\)AH=AB.sinB=3,6.sin62=3,18

BH=\(\sqrt{AB^2-AH^2}\)(pytago)=\(\sqrt{3,6^2-3,18^2}\)=1,69

\(_{\widehat{C}}\)=90-\(\widehat{B}\)=90-62=28\(^0\)

sinC=\(\dfrac{AB}{BC}\)\(\Rightarrow\)BC=\(\dfrac{AB}{sinC}\)=\(\dfrac{3,6}{sin28}\)=7,67

mà:CH=BC-BH=7,67-1,69=5,98

AC=\(\sqrt{BC^2-AB^2}\)(pytago)=\(\sqrt{7,67^2-3,6^2}\)=6.77

9)Ta có: \(\sqrt{x^2-6x+9}=5\)

\(\Leftrightarrow\sqrt{\left(x-3\right)^2}=5\)

\(\Leftrightarrow\left|x-3\right|=5\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=5\\x-3=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-2\end{matrix}\right.\)

Vậy: S={8;-2}

19) Ta có: \(\sqrt[3]{x^3+9x^2}=x+3\)

\(\Leftrightarrow x^3+9x^2=\left(x+3\right)^3\)

\(\Leftrightarrow x^3+9x^2=x^3+9x^2+27x+27\)

\(\Leftrightarrow27x=-27\)

hay x=-1

Vậy: S={-1}

9 tháng 9 2016

bạn khen thì tốt quá nhưng mình chưa học bài này!!!!

3 tháng 1 2022

thi thì bạn tự làm nha

3 tháng 1 2022

kiểm tra bạn nên tự làm 

a: 6/5-2/3=18/15-10/15=8/15

b: 9/7-5/8=72/56-35/56=37/56

c: 7/6-3/4=14/12-9/12=5/12

d: 9/8-8/9=81/72-64/72=17/72

e: 7/5-7/6=7(1/5-1/6)=7/30

f: 3/4-2/5=15/20-8/20=7/20

g: 4/7-5/6=24/42-35/42=-11/41

i: 6/13-5/11=66/143-65/143=1/143

k: 1-4/5=1/5

m: 2-5/9=18/9-5/9=13/9

n: 3-9/5=15/5-9/5=6/5

p: 4-3/4=16/4-3/4=13/4

22 tháng 2 2022

a) \(\dfrac{6}{5}-\dfrac{2}{3}=\dfrac{18}{15}-\dfrac{10}{15}=\dfrac{8}{15}\)

b) \(\dfrac{9}{7}-\dfrac{5}{8}=\dfrac{72}{56}-\dfrac{35}{56}=\dfrac{37}{56}\)

c) \(\dfrac{7}{6}-\dfrac{3}{4}=\dfrac{28}{24}-\dfrac{18}{24}=\dfrac{10}{24}=\dfrac{5}{12}\)

d) \(\dfrac{9}{8}-\dfrac{8}{9}=\dfrac{81}{72}-\dfrac{64}{72}=\dfrac{17}{72}\)

e) \(\dfrac{7}{5}-\dfrac{7}{6}=\dfrac{42}{30}-\dfrac{35}{30}=\dfrac{7}{30}\)

h) \(\dfrac{4}{7}-\dfrac{5}{6}=\dfrac{24}{42}-\dfrac{35}{42}=-\dfrac{11}{42}\)

i) \(\dfrac{6}{13}-\dfrac{5}{11}=\dfrac{66}{143}-\dfrac{65}{143}=\dfrac{1}{143}\)

k) \(1-\dfrac{4}{5}=\dfrac{5}{5}-\dfrac{4}{5}=\dfrac{1}{5}\)

m) \(2-\dfrac{5}{9}=\dfrac{18}{9}-\dfrac{5}{9}=\dfrac{13}{9}\)

n) \(3-\dfrac{9}{5}=\dfrac{15}{5}-\dfrac{9}{5}=\dfrac{6}{5}\)

p) \(4-\dfrac{3}{4}=\dfrac{16}{4}-\dfrac{3}{4}=\dfrac{13}{4}\)