a=3,b=4
[4/(√a+√b)(√a -√b)+(√a+√b)/√ab(√b-√a]÷(√a-√b)/√ab
=[4√ab/√ab(√a+√b)(√a -√b)-(√a+√b)^2/√ab(√a-√b)(√a+√b)]÷(√a-√b)/√ab
={[4√ab-(√a+√b)^2]/√ab(√a-√b)(√a+√b)}÷(√a-√b)/√ab
={[-(√a-√b)^2]/√ab(√a-√b)(√a+√b)}÷(√a-√b)/√ab
=-{[(√a-√b)]/√ab(√a+√b)}÷(√a-√b)/√ab
=1/(√a+√b)
=1/(2+√3)
=2-√3