\(\left\{{}\begin{matrix}0,5x-1,5y=1\\-x+3y=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x-3y=2\\-x+3y=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=3y+2\\-\left(3y+2\right)+3y=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=3y+2\\-3y-2+3y=2\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=3y+2\\-2=2\end{matrix}\right.\)

=> Hpt vô nghiệm 

0,5x - 1,5y = 1 (1)

-x + 3y = 2 (2)

Từ (2) ta có:

x = 3y - 2 (3)

Thế (3) vào (1), ta có:

0,5(3y - 2) - 1,5y = 1

1,5y - 1 - 1,5y = 1

0y = 1 + 1

0y = 2 (vô lý)

Vậy 

??

2 bạn nhé.

Ta gọi số cần tìm là: \(\overline{4bc}\)

Khi xóa đi chữ số 4 ta còn lại: \(\overline{bc}\)

Khoảng cách giữa \(\overline{4bc}\) và \(\overline{bc}\) là: 400

Hiệu số phần bằng nhau là: 9 - 1 = 8 (phần)

Số có 3 chữ số ban đầu là: 400 : 8 x 9 = 450

Vậy số cần tìm là: 450

\(\dfrac{144}{56}\)

cảm ơn

\(\left(\dfrac{-4}{9}\right)^2=\dfrac{16}{81}\Rightarrow x=2\) 

\(\left(-\dfrac{1}{3}\right)^3=\dfrac{-1}{27}\Rightarrow x=1\)

\(\left(-\dfrac{1}{3}\right)^4=\dfrac{1}{81}\Rightarrow x=1\)

\(\left(-\dfrac{4}{9}\right)^x=\dfrac{16}{81}\\ \left(-\dfrac{4}{9}\right)^x=\left(\dfrac{4}{9}\right)^2\\ \left(-\dfrac{4}{9}\right)^x=\left(-\dfrac{4}{9}\right)^2\\ x=2\\ -----------\\ \left(-\dfrac{1}{3}\right)^{2x+1}=-\dfrac{1}{27}\\ \left(-\dfrac{1}{3}\right)^{2x+1}=\left(-\dfrac{1}{3}\right)^3\\ 2x+1=3\\ 2x=3-1=2\\ x=\dfrac{2}{2}=1\\ -----------\\ \left(-\dfrac{1}{3}\right)^{3x+1}=\dfrac{1}{81}\\\left(-\dfrac{1}{3}\right)^{3x+1}=\left(\dfrac{1}{3}\right)^4\\ \left(-\dfrac{1}{3}\right)^{3x+1}=\left(-\dfrac{1}{3}\right)^4\\ 3x+1=4\\ 3x=4-1=3\\ x=\dfrac{3}{3}=1\)

\(\left(\dfrac{7}{5}\right)^x=\dfrac{49}{25}\Leftrightarrow\left(\dfrac{7}{5}\right)^x=\left(\dfrac{7}{5}\right)^2\Leftrightarrow x=2\)

Không sử dụng dấu tương đương nhé!

(145.99+145)-(143.102-143)

=(145.99+145.1)-(143.102-143.1)

=[145.(99+1)]-[143.(102-1)]

=[145.100]-[143.101]

=14500-14443

=57

54.47-47.53-20-27

=47.(54-53)-(20+27)

=47.1-47

=47-47

=0

(145 x 99 + 145) - (143 x 102 - 143)

= 145 x (99 + 1) - 143 x (102 - 1)

= 145 x 100 - 143 x 101

= 14500 - 143 x (100 + 1)

= 14500 - 14300 - 143

= 200 - 143

= 57

_________________________

54 x 47 - 47 x 53 - 20 - 27

= 54 x 47 - 47 x 53 - 47

= 47 x (54 - 53 - 1)

= 47 x 0

= 0

c:

`a)x^2 - 4+x(x-2)=0`

`<=>(x-2)(x+2)+x(x-2)=0`

`<=>(x-2)[(x+2)+x]=0`

`<=>(x-2)(x+2+x)=0`

`<=>(x-2)(2x+2)=0`

`<=>x-2=0` hoặc `2x+2=0`

`<=>x=2` hoặc `x=-1`

Vậy `x=-1` hoặc `x=2`

`b)(2x+1)^2 - 4x^2=0`

`<=>[(2x+1)-2x][(2x+1)+2x]=0`

`<=>(2x+1-2x)(2x+1+2x)=0`

`<=>1(4x+1)=0`

`<=>4x+1=0`

`<=>4x=-1`

`<=>x=-1/4`

Vậy `x=-1/4`

`c)x^2 - 75x=0`

`<=>x(x-75)=0`

`<=>x=0` hoặc `x-75=0`

`<=>x=0` hoặc `x=75`

Vậy `x=0` hoặc `x=75`

a, \(x^2-4+x\left(x-2\right)=0\Leftrightarrow\left(x-2\right)\left(x+2\right)+x\left(x-2\right)=0\\ \Leftrightarrow\left(x-2\right)\left(x+2+x\right)=0\Leftrightarrow x=2;x=-1\)

b, \(\left(2x+1\right)^2-4x^2=0\Leftrightarrow\left(2x+1\right)^2-\left(2x\right)^2=0\)

\(\Leftrightarrow\left(2x+1-2x\right)\left(2x+1+2x\right)=0\Leftrightarrow4x+1=0\Leftrightarrow x=-\dfrac{1}{4}\)

c, \(x^2-75x=0\Leftrightarrow x\left(x-75\right)=0\Leftrightarrow x=0;x=75\)