I can't imagine why the variable in the exponent isn't 'n'.
To me, that's the only way this makes sense, and I'm
going to handle it as if the exponent is (n - 1) .
First term: n = 1
A(1) = -2 · 5¹⁻¹ = -2 · 5⁰ = -2 · 1 = -2 .
Fourth term: n = 4
A(4) = -2 · 5⁴⁻¹ = -2 · 5³ = -2 · 125 = -250 .
Eighth term: n = 8
A(8) = -2 · 5⁸⁻¹ = -2 · 5⁷ = -2 · 78,125 = -156,250 .
The first choice on the list looks like the correct one.