SASMO 2018 Secondary 3 (Grade 9) Contest Question 8

The following calculations lead to the conclusion that x = 0. Which one of the
following transition steps is wrong?
Ne a a
V0 vn vt
i —=— 1 = — 2.
Wren nde
va
=a 3
Vav-1 a (3)
vav-Iv-1 = Vir (4)
vii (-1) = Va (5)
-viava =› 0=Vitvn (©)
vr=0 =› n=0 (7)