-1^(8/17) = 5e^(zt) - e^(5zt)     | -1^n = -1 , falls n!=0
-1 = (e^(zt))^5 - e^(5zt)     | (a^n)^m = a^(n*m)
-1 =  e^(5zt) - e^(5zt)
-1 = 0