The sum if the geometric sequence given by:
an=-2(3)^(n-1)
will be:
when:
n=1
an=-2
when n=2
a2=-6
when n=3
a3=-18
when n=4
a4=-54
when n=5
a5=-162
when n=6
a6=-486
when n=7
a7=-1458
when n=8
a8=-4374
thus the summation of the term will be:
Sn=(-4374+-1458+-486+-162+-54+-18+-6+-2)
Sn=-6560
the answer is -6560
Answer
y = (1/4)x - 5 or 4y - x + 20 = 0
Explanation
To get the rule required, we interpret the sentence and write it in a mathematical form.
5 less than one fourth of x is y
one fourth of x ⇒ (1/4)x
5 less than one fourth of x is y ⇒ (1/4)x - 5 = y
y = (1/4)x - 5
4y = x - 20
4y - x + 20 = 0
