a) 2/7 + x =  -0,75

x= - 3/4 - 2/7

x= 21/28 - 8/28

x = 13/28

Vậy x = 13/28

b) -4 1/5 - x = 2,25

-21/5 - x = 2,25

-x = 2,25 + 21/5

-x = 45/20 + 21/5

-x = 45/20 + 84/20

-x = 84/20

x = -84/20

Vậy x = -84/20

c) x : 8,5 = -2,2

x = -2,2 . 8,5

x = -18,7

Vậy x = -18,7

d) ( 2x/5 - 1 ) : ( -5 ) = 1/7

2x/5 - 1 = 1/7 . ( -5 )

2x/5 - 1 = -5/7

2x/5 = -5/7 + 1

2x/5 = -5/7 + 7/7

2x/5 = 2/7

x = 2/7 : 2/5

x = 2/7 . 5/2

x = 5/7

Vậy x = 5/7

s m ngu z

A x=-0,75-2/7

B x=-21/5-2,25

a) x= -0,75 - 2/7 = -29/28

c) x = 2,2 . 8,5 = 18.7

\(\text{VT = }10,07-3,927+3,63-\frac{3}{20}=9,623\)

\(VP=13,8-\frac{3}{5}+\frac{7}{50}=13,34\)

\(\text{Vì }x\in Z\Rightarrow x\left\{10;11;12;13\right\}\)

\(17.8+51.4=34.4+51.4=4\left(51+34\right)=4.84=336\) \(2.2.3.5.19=\left(2.5\right).\left(3.19\right).2=10.2.57=570.2=1140\) \(54.275+825.15+275=54.275+45.275+275=275\left(54+45+1\right)=100.275=27500\) \(\frac{167.198+98}{198.168-100}=\frac{167.198+98}{198.167+198-100}=\frac{167.198+98}{167.198+98}=1\)

\(\frac{1}{n}-\frac{1}{n+k}=\frac{k}{n\left(n+k\right)}\Rightarrow\frac{1}{1.2}+\frac{1}{2.3}+.....+\frac{1}{2019.2020}=1-\frac{1}{2}+\frac{1}{2}-....-\frac{1}{2020}=1-\frac{1}{2020}=\frac{2019}{2020}\)

a) 17 x 8 + 51 x 4

= 17 x 4 x 2 + 17 x 3 x 4

= 17 x 4 x ( 2 + 3 )

= 14 x 4 x 5

= 14 x 20

= 280

b) 2 x 2 x 3 x 5 x 19

= ( 2 x 5 ) x ( 3 x 19 ) x 2

= 10 x 57 x 2

= 570 x 2

= 1140

c) 54 x 275 + 825 x 15 + 275

= 54 x 275 + 275 x 3 x 15 + 275 x 1

= 54 x 275 + 275 x 45 + 275 x 1

= 275 x ( 54 + 45 + 1 )

= 275 x 100

= 27500

d) 100 - 99 + 98 - 97 + 96 - 95 + 94 - 93 + ... + 4 - 3 + 2

= (100 - 99) + (98 - 97) + (96 - 95) + (94 - 93) + ... + (4 - 3) + 2

= (1 + 1 + ... + 1) + 2

( 49 số 1 )

= 49 + 2

= 51

k) 1,5 + 2,5 + 3,5 + 4,5 + 5,5 + 6,5 + 7,5 + 8,5

= ( 1,5 + 8,5 ) + ( 2,5 + 7,5 ) + ( 3,5 + 6,5 ) + ( 4,5 + 5,5 )

= 10 + 10 + 10 + 10

= 40

a) 11 1/4- 2 5/7 - 5 1/4

11 1/4 - 5 1/4 - 2 5/7

( 11 -5) + ( 1/4 -1/4) -2 5/7

6 +0 -2 5/7

6- 2 5/7

5+1 - 2 5/7

( 5-2) + ( 1-5/7)

3+( 7/7 -5/7)

3 + 2/7

3 2/7

3+

a) -5(x - 3) - 2(5 - 3x) = -(x - 1)

=> -5x + 15 - 10 + 6x = -x + 1

=> x + 5 = -x + 1

=> x + x = 1 - 5

=> 2x = -4

=> x = -4 : 2

=> x = -2

\(-5\left(x-3\right)-2\left(5-3x\right)=-\left(x-1\right)\)

\(\Leftrightarrow-5x+15-10+6x=-x+1\)

\(\Leftrightarrow x+5=1-x\)

\(\Leftrightarrow2x=-4\)

\(\Leftrightarrow x=-4\div2\)

\(\Leftrightarrow x=-2\)

Cảm ơn

Bài 1 tự làm!

Bài 2:

a, \(\left(3x-4\right)\left(x-1\right)^3=0\Rightarrow\left[{}\begin{matrix}3x-4=0\\\left(x-1\right)^3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{4}{3}\\x-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{4}{3}\\x=1\end{matrix}\right.\)

b, \(2^{2x-1}:4=8^3\Rightarrow2^{2x-1}:2^2=2^9\)

\(\Rightarrow2x-1-2=9\Rightarrow2x-3=9\Rightarrow2x-12\Rightarrow x=6\)

c, Đề chưa rõ

d, \(\left(x+2\right)^5=2^{10}\Rightarrow\left(x+2\right)^5=4^5\Rightarrow x+2=4\Rightarrow x=2\)

e, \(\left(3x-2^4\right).7^3=2.7^4\Rightarrow3x-2^4=2.7^4:7^3\Rightarrow3x-16=2.7=14\)

\(\Rightarrow3x=14+16=30\Rightarrow x=\dfrac{30}{3}=10\)

f, \(\left(x+1\right)^2=\left(x+1\right)^0\Rightarrow\left(x+1\right)^2=1\) (vì x⁰ = 1)

\(\Rightarrow x+1=1\Rightarrow x=0\)

Làm phần c nè!

c, \(\left(x-5\right)^4=\left(x-5\right)^6\Rightarrow\left(x-5\right)^4-\left(x-5\right)^6=0\)

\(\Rightarrow\left(x-5\right)^4.\left(x-5\right)^2=0\)

\(\Rightarrow x-5=0\Rightarrow x=5\)