Answer:
The common difference d in the given sequence is -17
Step-by-step explanation:
We need to find the common difference d of the following sequence 9 -8 -25 -42 -59
We have a₁ = 9
and a₂ = -8
The formula used is: 
By putting values we can find the value of d
We have n=2, a₂ = -8, a₁ = 9 and we need to find d

So, the common difference d in the given sequence is -17
Vertex form is y = -(x+4)^2+9
Letter C. Is correct I think, hope this helped.
A.the measures of the angles must be equal
Vertical Angles- are the angles opposite of each other when two lines cross. They are always equal.