ANSWER
No, because there is no common ratio
EXPLANATION
The given sequence is
-1, 1, 4, 8
If this sequence is geometric, then there should be a common ratio among the consecutive terms.

Hence the sequence
-1, 1, 4, 8
is not a geometric sequence.
Answer:
its 20 2/3
Step-by-step explanation:
bc 4 * 5 which equals 20 and then just add a 2/3
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Ad - bc = f......for d
add bc to both sides
ad = f + bc
divide both sides by a
d = (f + bc) / a