For each situation, find the sample space

What is the explicit formula for this sequence? -7, -4, -1, 2, a.) an = 8 + (b - 1)3 b.) an = -7 + (n - 1)3 c.) an = 3 + (n -1) (-7) d.) an = -7 + (n - )

What is the value of x when x + 7 = 21?

Find the missing factor. write your answer inexponential form.9^2=9^4×