25(35+X)+20*Y²=30X² 20+60Y=60X 聯立方程式求解X及Y=? 我要計算過程!感謝?

25(35 + x) + 20y² = 30x² ...... [1]
20 + 60y = 60x ...... [2]

由[2]：
(1/3) + y = x
y = x ‒ (1/3) ...... [3]

將 [3] 代入 [1] 中：
25(35 + x) + 20[x ‒ (1/3)]² = 30x²
875 + 25x + 20x² ‒ (40/3)x + (20/9) = 30x²
175 + 5x + 4x² ‒ (8/3)x + (4/9) = 6x²
1575 + 45x + 36x² ‒ 24x + 4 = 54x²
18x² ‒ 21x ‒ 1579 = 0
x = (7 ± 3√1409)/12

代入 [3] 中：
y = [(7 ± 3√1409)/12] ‒ (1/3)
y = (1 ± √1409)/4

答案：x = (7 + 3√1409)/12, y = (1 + √1409)/4
或：x = (7 ‒ 3√1409)/12, y = (1 ‒ √1409)/4