Level:
Project ID:
1003112804
Accepted:
1
Clonable:
0
Easy:
0
The third term of a geometric sequence is \( -5 \) and the eighth term is \( -5 \). \( s_5 \) is the sum of the first five terms and \( q \) is the common ratio of this sequence. Choose the formula which is not valid for this sequence:
\( s_5=-5\cdot\frac{q^5-1}{q-1} \)
\( s_5=-25 \)
\( s_5=5\cdot a_1 \)
\( s_5=5\cdot a_3 \)
\( s_5=5\cdot(-5) \)