Question

(xy)/(x+y)=6,(xy)/9x+4y=1用倒数法求解

Answer 1

(xy)/(x+y)=6 (xy)/(9x+4y)=1

(x+y)/(xy)=1/6 (9x+4y)/(xy)=1

1/y+1/x =1/6 (1) 9/y+4/x =1 (2)

(1)式*9-(2)式 得5/x=1/2 x=5*2=10

代入(1)式 1/y+1/10 =1/6 30/y+3=5 y=15