1 B

2 D

3 C

4 A

5 C

6 C

7 B

8 A

9 B

10 C

a. 2/5 
b. 5/4

a, `2/5 xx 3/7 +2/5 xx 4/7 = 2/5 xx (3/7+4/7)=2/5 xx 7/7 =2/5xx1=2/5`

b, `5/8xx5/4-5/8xx3/4=5/8xx(5/4-3/4)=5/8xx2/4=5/8xx1/2=5/16`

a, 2/5 x (3/7 + 4/7)
= 2/5 x 7/7 
= 49/35 

b, 5/8 x (5/4 - 3/4)
= 5/8 x 2/3
= 10

đó là kết quả đó!
 

\(\dfrac{27}{35}\):\(\dfrac{9}{7}\)=\(\dfrac{3}{5}\).

\(\dfrac{27}{35}\div\dfrac{9}{7}=\dfrac{27}{35}\times\dfrac{7}{9}=\dfrac{3}{5}\) 

` 27/35 : 9/7 = 27/35 . 7/9 = 3/5`

Đặt \(2017-x=m,2019-x=n\)

\(\rightarrow m+n=2x-4036\)

Phương trình ban đầu trở thành :

\(m^3+n^3=\left(m+n\right)^3\)

\(\rightarrow3mn.\left(m+n\right)^3=0\)

\(\rightarrow\left(2017-x\right)\left(2019-x\right)\left(2x-4036\right)=0\)

\(\rightarrow\left[{}\begin{matrix}x=2017\\x=2018\\x=2019\end{matrix}\right.\)

Vậy \(S=\left\{2017;2018;2019\right\}\)

(2017-X)³+(2019-X)³+(2X-4036)³=0

<=>(2017-x).(2018-x).(2019-x)=0

<=>x=2017

x=2018

x=2019

#YQ

 A = x² - 7x + 6

    =(x-1)(x-6)

cũng dễ thôi mà!!!

a, \(x^2-7x+6=x^2-x-6x+6\)

\(=x\left(x-1\right)-6\left(x-1\right)\)

\(=\left(x-6\right)\left(x-1\right)\)

b, \(|2x+1|-5x=3\)(*)

TH1: \(2x+1\ge0=>x\ge\frac{-1}{2}\)

PT(*) <=> \(2x+1-5x=3=>x=\frac{-2}{3}\)(thỏa mãn)

TH2: \(2x+1< 0=>x< \frac{-1}{2}\)

PT(*) <=> \(-2x-1-5x=3=>x=\frac{4}{7}\)(ko thỏa mãn)

Vậy phương trình có tập nghiệm S=\(\left\{\frac{-2}{3}\right\}\)

A = x² - x - 6x +6
=> A = (x²-x)-(6x-6)
=> A = x(x-1)-6(x-1)
=> A = (x-1)(x-6)

Sao vậy?

what the hell

điên à?

a: \(\Leftrightarrow\left(5x+\dfrac{3}{2}\right):\dfrac{8}{15}=\dfrac{25}{12}-\dfrac{5}{6}=\dfrac{25}{12}-\dfrac{10}{12}=\dfrac{15}{12}=\dfrac{5}{4}\)

\(\Leftrightarrow5x+\dfrac{3}{2}=\dfrac{5}{4}\cdot\dfrac{8}{15}=\dfrac{40}{60}=\dfrac{2}{3}\)

\(\Leftrightarrow5x=\dfrac{2}{3}-\dfrac{3}{2}=\dfrac{4-9}{6}=\dfrac{-5}{6}\)

hay x=-1/6

b: \(\Leftrightarrow\dfrac{1}{4}\left(2-\dfrac{1}{2}x\right)=\dfrac{5}{2}-\dfrac{1}{4}=\dfrac{10}{4}-\dfrac{1}{4}=\dfrac{9}{4}\)

=>2-1/2x=9

=>1/2x=-7

hay x=-14

c: \(\Leftrightarrow\left(x-7\right)^2=144\)

=>x-7=12 hoặc x-7=-12

=>x=19 hoặc x=-5

d: \(\Leftrightarrow4x+2=3x-15\)

hay x=-17

e: =>1/6x=-4

hay x=-24