Can she get some help

Step-by-step explanation:

the formula for an arithmetic sequence that is explicit is

 where is the first term (so -1), and d is the common difference (-2). n is the number position in the sequence. As soon as we find the formula or model for this sequence we can find any number term we want. Filling in the formula:

and we'll clean that up just a bit:

(I just distributed through the parenthesis) and a bit more to

and if we want the 21st term, fill in a 21 for n:

and

so

x = ± 6i

step-by-step explanation:

x^2 = -36

take the square root of each side

sqrt(x^2) = sqrt(-36)

we know sqrt(ab) = sqrt(a) sqrt(b)

x = ±sqrt(36) sqrt(-1)

we know that sqrt (-1) = i

x = ± 6i

there is nothing below so i cannot

step-by-step explanation: