In a circumference question that asks for the diameter of a semi circle do you divide the final circumference by 2 and for a quarter circle do you divide it by 4

Which of the following is the formula for the sequence graphed below

What is the base of 1/9 to the power of 2

Hell . what are the solutions to `10x^2 - 38x - 8 = 0`? is this when i find the factors and use the numbers within the factors to determine the zeros? i hope that made sense lol