1 câu trả lời
Lay ptrinh duoi tru ptrinh tren ta co Dat $a = \sqrt{x}, b = \sqrt{y}$. Khi do, he tro thanh $$\begin{cases} a^2 b + b^2 a = 30 (1)\\ a^3 + b^3 = 35(2) \end{cases}$$ Lay 3.(1)+(2) ta co $$3a^2b + 3b^2 a + a^3 + b^3 = 3.30 + 35$$ hay $$15a^2 - 75a + 90 = 0$$ Vay $a = 2$ hoac $a = 3$. Tuong ung la $b = 3$ hoac $b = 2$. Vay $(a,b) = (2,3)$ hoac $(a,b) = (3,2)$. Vay (x,y) = (4,9) hoac (x,y) = (9,4).
