Answer:
219 677 417 263; Geometric
Step-by-step explanation:
Consecutive terms alternate in sign and differ by a factor of 3.
That tells us this is a geometric sequence.
The formula for the nth term of a geometric sequence is
aₙ = a₁rⁿ⁻¹
a₁ = 7
a₂ = -21
a₃ = 63
a₄ = -189
The common factor r is -3.
a₂₃ = 7(-3)²² = 219 677 417 263
