數學二次方程

xy=150---1
(x+6)(y+6)=150+186---2

(1)------------ x = 150/y ---3

subst 3 into 2 (150/y + 6)(y+6) = 150+186
150+ 900/y + 6y + 36 = 336
900/y + 6y = 150
6y^2 + 900 = 150y
6y^2 - 150y + 900 = 0
y^2 - 25y + 150 = 0
(y - 10)(y - 15) = 0
y = 10 or y = 15

2007-11-21 17:46:59 補充：
未答xy = 10 or y = 15when y = 10xy=150x = 15when y = 15xy=150x = 10下面個個人.....抄都抄到咁...仲話你做

2007-11-21 17:47:21 補充：
我話Ryan Mak

xy=150
x = 150/y ------(1)
(x+6)(y+6)=150+186---(2)

put 1 into 2
(150/y + 6)(y+6) = 150+186
150+ 900/y + 6y + 36 = 336
900/y + 6y = 150
6y^2 + 900 = 150y
6y^2 - 150y + 900 = 0
y^2 - 25y + 150 = 0
(y - 10)(y - 15) = 0
y = 10 or y = 15
x = 15 or y =10

xy=150---1
(x+6)(y+6)=150+186---2

(1)------------ x = 150/y ---3

subst 3 into 2 (150/y + 6)(y+6) = 150+186
150+ 900/y + 6y + 36 = 336
900/y + 6y = 150
6y^2 + 900 = 150y
6y^2 - 150y + 900 = 0
y^2 - 25y + 150 = 0
(y - 10)(y - 15) = 0
y = 10 or y = 15