Question

express 10-4 sqrt-18 as complex number in a+b i form whatt is the imaginary term

Answer 1

Interpretation 1 (most likely): you mean 10 − 4√(−18).

√(−18) = i√18 = 3√2 · i, so
10 − 4√(−18) = 10 − 4(3√2 i) = 10 − 12√2 i.

In a + bi form: a = 10, b = −12√2. The imaginary term is −12√2 i (imaginary coefficient −12√2).

If you instead meant 10 − 4√18 (no negative under the root), the number is real: 10 − 12√2 and the imaginary term is 0.