2xy−x+y=3

\(\Rightarrow 4 x y - 2 x + 2 y = 6\)

\(\Rightarrow 2 x \left(\right. 2 y - 1 \left.\right) + \left(\right. 2 y - 1 \left.\right) = 5\)

\(\Rightarrow \left(\right. 2 x + 1 \left.\right) \left(\right. 2 y - 1 \left.\right) = 5\)

Do \(x , y \in Z^{+}\) nên ta có bảng sau:

Vậy cặp số \(\left(\right. x ; y \left.\right)\) là \(\left(\right. 0 ; 3 \left.\right) ; \left(\right. 2 ; 1 \left.\right)\)

S O S

1 + 3 + 5 + 7 + ... + ( 2x - 1 ) = 225

=> ( 1 + 2n - 1 ) . n : 2 = n²

Suy ra 1 + 3 + 5 + 7 + ... + ( 2x - 1 ) = n²

Ta có : 225 = 3² . 5² = ( 3 . 5 )² = 15²

Vậy n = 15

= 48 + 288 : ( x - 3 )² = 50 

288 : ( x - 3 )² = 50 - 48

288: ( x - 3 )²= 2

(x - 3 )²= 288 : 2

(x - 3)²= 144

(x - 3)² = 12²

x - 3 = 12 

x = 12 + 3 = 15

A=301​+421​+561​+...+1321​

\(A = \frac{1}{5.6} + \frac{1}{6.7} + \frac{1}{7.8} + . . . + \frac{1}{11.12}\)

\(A = \frac{1}{5} - \frac{1}{6} + \frac{1}{6} - \frac{1}{7} + \frac{1}{7} - \frac{1}{8} + . . . + \frac{1}{11} - \frac{1}{12}\)

\(A = \frac{1}{5} - \frac{1}{12}\)

\(A = \frac{12}{60} - \frac{5}{60} = \frac{7}{60}\)

Tỉ lệ thể tích cũng giống tỉ lệ về số mol nhé em