Lesben 1) log2 (x+5) - log2 (x-5)=1
    log2 (x+5)/(x-5) = log2 2
   (x+5)/(x-5)=2
   x+5 = 2.(x-5)
   x=15
2)V(x-2)-V(x-3) =1
   V(x-2) = 1+V(x-3
   x-2 = 1+2.V(x-3) +x -3
   2.V(x-3)=0, V(x-3)=0, x-3=0, x=3
3)16ˇx +8.4ˇx -9=0
   (4ˇx)ˇ2 +8.4ˇx -9=0 , 4ˇx=t
   tˇ2 +8t-9=0, t1=1, t2=-9
   a)4ˇx =1, 4ˇx = 4ˇ0, x=0
   b)4ˇx = -9 eto nelzja ( 4ˇx bcegda bolše čem 0)
4)lg x lg y = 2, x-10y = 900
   lg(x/y)=lg 100, x/y = 100, x = 100y
100y-10y=900, y=10