<span>42.7−<span>(<span>−12.4</span>)
</span></span><span>=<span>42.7−<span>(<span>−12.4</span>)
</span></span></span><span>=<span>42.7+12.4
</span></span><span>=<span>55.1</span></span>
The explicit formula for arithmetic sequence is:
an=a+(n-1)d
where:
a=first term
d=common difference
given:
a3=22
a(17)=-20
substituting this in our equation we get:
22=a+(3-1)d
22=a+2d
a=22-2d........i
also:
-20=a+(17-1)d
-20=a+16d.....ii
but substituting i in ii we get:
-20=22-2d+16d
-20-22=14d
-42=14d
d=-3
but:
a=22-2d
a=22-2(-3)
a=28
thus the formula will be:
an=28-3(n-1)
thus the first term will be 28
the 2nd term will be:
a2=28-3(2-1)
a2=25
the 3rd term will be:
a3=28-3(3-1)
a3=28-6
a3=22
a4=28-3(4-1)
a4=28-9
a4=15
a5=28-3(5-1)
a5=28-3(4)
a5=28-12
a5=15
58.3 I think....hope it helps
Here, we may use Geometric Progression
The sequence follows as:
27, 18,12,...
The first term (a)= 27
27/18 = 18/12
common ratio = 1.5
Let fourth term be x
Therefore , 12/x = 1.5
=> x= 12/1.5 = 8
