\(\left(\frac{2}{31\times33}+\frac{2}{33\times35}+...+\frac{2}{39\times41}\right)\times2542-2,04:x=19\)

\(\Rightarrow\left(\frac{1}{31}-\frac{1}{33}+\frac{1}{33}-\frac{1}{35}+...+\frac{1}{39}-\frac{1}{41}\right)\times2542-2,04:x=19\)

\(\Rightarrow\left(\frac{1}{31}-\frac{1}{41}\right)\times2542-2,04:x=19\)

\(\Rightarrow\frac{10}{1271}\times2542-2,04:x=19\)

\(\Rightarrow20-2,04:x=19\)

\(\Rightarrow2,04:x=20-19\)

\(\Rightarrow2,04:x=1\)

\(\Rightarrow x=2,04:1\)

\(\Rightarrow x=2,04\)

Vậy x = 2,04

\(\left(\frac{2}{31\text{ x }33}+\frac{2}{33\text{ x }35}+...+\frac{2}{39\text{ x }41}\right)\text{ x }2542-2,04\text{ : }x=19\)

\(\left(\frac{1}{31}-\frac{1}{33}+\frac{1}{33}-\frac{1}{35}+...+\frac{1}{39}-\frac{1}{41}\right)\text{ x }2542-2,04\text{ : }x=1\)

\(\left(\frac{1}{31}-\frac{1}{41}\right)\text{ x }2542-2,04\text{ : }x=1\)

\(\frac{10}{1271}\text{ x }2542-2,04\text{ : }x=1\)

\(20-2,04\text{ : }x=1\)

\(2,04\text{ : }x=20-1\)

\(2,04\text{ : }x=19\)

\(x=2,04\text{ : }19\)

\(x=\frac{51}{475}\)

\(\left(\frac{2}{31\text{ x }33}+\frac{2}{33\text{ x }35}+...+\frac{2}{39\text{ x }41}\right)\text{ x }2542-2,04\text{ : }x=19\)

\(\left(\frac{1}{31}-\frac{1}{33}+\frac{1}{33}-\frac{1}{35}+...+\frac{1}{39}-\frac{1}{41}\right)\text{ x }2542-2,04\text{ : }x=19\)

\(\left(\frac{1}{31}-\frac{1}{41}\right)\text{ x }2542-2,04\text{ : }x=19\)

\(\frac{10}{1271}\text{ x }2542-2,04\text{ : }x=19\)

\(20-2,04\text{ : }x=19\)

\(2,04\text{ : }x=20-19\)

\(2,04\text{ : }x=1\)

\(x=2,04\text{ : }1\)

\(x=2,04\)

\(1235\text{×}6789\text{×}\left(630-315\text{×}2\right)\)

\(=1235\text{×}6789\text{×}\left(630-630\right)\)

\(=1235\text{×}6789\text{×}0=0\)

\(\left(100+67\right)\text{×}67+\left(200-38\right)\text{×}33\)

\(=167\text{×}67+167\text{×}33\)

\(=167\text{×}\left(67+33\right)\)

\(=167\text{×}100=16700\)

\(72+36\text{×}2+24\text{×}3+18\text{×}4+12\text{×}2+168\)

\(=72+72+72+72+24+168\)

\(=\left(72\text{×}4\right)+24+168=288+24+168=480\)

a) \(1235\times6789\times\left(630-630\right)\)

\(=1235\times6789\times0\)

\(=1235\times0\)

\(=0\)

b) \(167\times67+167\times33\)

\(=167\times\left(67+33\right)\)

\(=167\times100\)

=16700

đây nhé

=33 x ( 7+2 ) 

= 33 x   9

= còn lại tự tính

=33 nhân ( 7+2)

=33 nhân 9

=  297

mik đâu bảo bạn tính đâu

mik bảo có thể chuyển biểu thức đó thành biểu thức nào mà?

\(\dfrac{15}{17}\)

\(=\dfrac{15}{17}\left(\dfrac{45}{33}-\dfrac{12}{33}\right)=\dfrac{15}{17}\)

15/17

a) 70 - 5 ( X-3)=45

5(x-3)=70-45

5(X-3)= 25

x-3=25:5

X-3=5

X=5+3=8

B) 3^x-12=15

3^x=12+15

3^x=27

3^x=3^3

=>x = 3

Tiếp phần kia

c) bn làm như sau:

a) \(70-5\left(x-3\right)=45\)

\(5\left(x-3\right)=70-45=25\)

\(x-3=\frac{25}{5}=5\)

\(x=8\)

b) \(3^x-12=15\)

\(3^x=15+12=27=3^3\)

\(\Rightarrow x=3\)

c) \(3^{x+2}+2\cdot3^x=3^{33}\cdot33\)

\(3^x\left(3^2+2\right)=3^{34}\cdot11\)

\(3^x\cdot11=3^{34}\cdot11\)

\(3^x=3^{34}\)

\(\Rightarrow x=34\)

30

30

30

1. 3x - 36 = 12 . 75 + 25 . 12

    3x - 36 = 12 . (75+25)

    3x - 36 = 12 . 100

    3x - 36 = 1200

    3x = 1200 + 36

    3x = 1236

=>  x = 1236 : 3 = 412

câu 1 thôi nhá bạn

3x - 36 = 12 . 75 + 25 . 12

3x - 36 = 12 . (75 + 25)

3x - 36 = 1200

3x = 1164

x = 388

x : 2 - 12 = 33 . 40 + 33 . 59 + 33

x : 2 - 12 = 33 . 40 + 33 . 59 + 33 . 1

x : 2 - 12 = (40 + 59 + 1)

x : 2 - 12 = 3300

x : 2 = 3288

x = 1644

(x - 4) . (9 - x) = 0

Thỏa mãn điều kiện\(\hept{\begin{cases}x=4\\x=9\end{cases}}\)

(x - 6) . (2020 - x) = 0

Thỏa mãn điều kiện\(\hept{\begin{cases}x=6\\x=2020\end{cases}}\)

x . (6 - x) = 0

Thỏa mãn điều kiện 6 - x = 0 

x = 6

(x - 3 - 12) . (20 - x) = 0

Thỏa mãn điều kiện \(x\le20\); 20 - x = 0

x = 20

không hiểu sao kia là ji

Phương trình có 2 nghiệm x1;x2 thì :\(\Delta>0\)

\(\Delta=9+4.6=33>0\)

Theo định lí Vi-ét,ta có :

\(\left\{{}\begin{matrix}x_1+x_2=3\\x_1.x_2=-6\end{matrix}\right.\)

Mà : \(x_1^2+x_2^2=\left(x_1+x_2\right)^2-2x_1.x_2=3^2+12=21\)

=> Chọn A.(21)