In this case the multiplicative inverse of the given complex no. is a complex no. which when multiplied by the given complex no. yields the product as unity.
Let the imaginary multiplicative inverse be z.
So, (4-3i)z = 1
or z = 1/(4-3i)
Rationalizing the R.H.S, we get,
z = (4+3i)/(4 - 3i)(4 + 3i)
or z = (4 + 3i)/(42 + 32)
or z = (4 + 3i)/25
or z = (4/25) + (3/25)i
So, the required multiplcative inverse is z = (4/25) + (3/25)i.