What states a rule using variables expression term or formula

Given the expression (7 ? 4i) ? (2 + 6i), perform the indicated operation and write the answer in the form a + bi.

Which is an x-intercept of the graphed function? (0, 4) (–1, 0) (4, 0) (0, –1)

Hi i’m not sure how to do question 20 if u could explain how to do it that’d b great