f4數,plz入

1 / (x + y) + 1 / y = 5 / 6 --- Equation 1
1 / y - 1 / (x + y) = 1 / 6 --- Equation 2
Equation 1 - Equation 2:
1 / (x + y) + 1 / y - 1 / y + 1 / (x + y) = 5 / 6 - 1 / 6
2 / (x + y) = 4 / 6
3 = x + y
y = 3 - x
substitute y = 3 - x and x + y = 3 into Equation 1
1 / 3 + 1 / (3 - x) = 5 / 6
1 / (3 - x) = 1 / 2
2 = 3 - x
x = 1
x + y = 3
1 + y = 3
y = 2

a)1/(x+Y)+1/Y=5/6
(1)(Y)+(X+Y)(1)/(X+Y)((Y)=5/6
(Y+X+Y)(6)=(5)(X+Y)(Y)
6(2Y+X) =5Y(X+Y)
12Y+6X =5y^2+5YX
5Y^2-12Y =6X-5YX

(5Y^2-12Y)/(6-5Y)=X

幫你搞左第一條equation，第二條自己試下啦
有錯請指出