Multiplying matrices on the left hand side

L.H.S =

= [6.0 + 2.2 + 4.x]

= [4 + 4x]

R.H.S = O (Ois the null matrix)

= 0

∴ L.H.S = R.H.S, so we get,

[4+4x] = O

4 + 4x = 0

4x = -4

x = -1

Hence value of x is equal to -1.