Question

$7 ^{log_{2}3 } -3^{log_{2}7}$

Answer 1

"турник"
a ^Logb c = c^ Logb a .
================
u =a ^Logb c⇒  Logb u =Logb c * Logb a .
v = c^ Logb a⇒  Logb v  =Logb a * Logb c.
Logb u = Logb v ⇔ u = v⇔ u- v =0.