Answer:
81
Step-by-step explanation:
I think it is correct.
According to short multiplication formula (square of difference)
(a - b)² = a² - 2ab + b²:
v² - 18v + ? = v² - 2 · 9v + ?
? = 9²
v² - 18v + 9² = (v - 9)²
9² = 81
The answer is 81.
