Find the value of c that completes the square x^2-6x+c

please help me with the math problem and show me how to do these kinds.

Thank you.

If the discriminant if a quadratic equation is 4 which statement describes the roots?

The evening newspaper is delivered at a random time between 5: 30 and 6: 30 pm. dinner is at a random time between 6: 00 and 7: 00 pm. each spinner is spun 30 times and the newspaper arrived 19 times before dinner. determine the experimental probability of the newspaper arriving before dinner.

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