Write the explicit formula for the geometric sequence.
a1 = -5 a2 = 20 a3 = -80
An explicit formula for a geometric sequence is: tn = t1 · rn - 1
where t1 is the first term = -5 r is the common ratio = -4
tn is the nth term (leave it in the formula) n is the number of the term (leave it in the formulat)
so the formula is tn = -5 · (-4)n - 1 <--- answer!
You can find the common ratio by dividing the second term by the first term: 20 ÷ -5 = -4
An explicit formula for a geometric sequence is: tn = t1 · rn - 1
where t1 is the first term = -5 r is the common ratio = -4
tn is the nth term (leave it in the formula) n is the number of the term (leave it in the formulat)
so the formula is tn = -5 · (-4)n - 1 <--- answer!
You can find the common ratio by dividing the second term by the first term: 20 ÷ -5 = -4