a/b=3/4 .(1)
b/c=3/2 .(2)
c/d=4/5 .(3)
由(1)得:a=3b/4 .(4)
由(2)得:c=2b/3 .(5)
(2)*(3)得:b/d=6/5,d=5b/6 .(6)
将(4)、(5)、(6)代入ac/(b²+d²)得:
ac/(b²+d²)= 3b/4 * 2b/3 /[b²+(5b/6)²]= 18/61
a/b=3/4 .(1)
b/c=3/2 .(2)
c/d=4/5 .(3)
由(1)得:a=3b/4 .(4)
由(2)得:c=2b/3 .(5)
(2)*(3)得:b/d=6/5,d=5b/6 .(6)
将(4)、(5)、(6)代入ac/(b²+d²)得:
ac/(b²+d²)= 3b/4 * 2b/3 /[b²+(5b/6)²]= 18/61