数学题当(a-2b)÷(a+2b)+4时,求代数式3(a-2b)÷4(a+2b)+3(a+2b)÷(a-2b)的值

当(a-2b)÷(a+2b)=4时
(a+2b)÷(a-2b)=1/4
3(a-2b)÷4(a+2b)+3(a+2b)÷(a-2b)
=3/4*[(a-2b)÷(a+2b)]+3[(a+2b)÷(a-2b)]
=3/4*4+3*1/4
=3.75