Answer:
Step-by-step explanation:
As the statement is ‘‘if and only if’’ we need to prove two implications
is surjective implies there exists a function
such that
.- If there exists a function
such that
, then
is surjective
Let us start by the first implication.
Our hypothesis is that the function
is surjective. From this we know that for every
there exist, at least, one
such that
.
Now, define the sets
. Notice that the set
is the pre-image of the element
. Also, from the fact that
is a function we deduce that
, and because
the sets
are no empty.
From each set
choose only one element
, and notice that
.
So, we can define the function
as
. It is no difficult to conclude that
. With this we have that
, and the prove is complete.
Now, let us prove the second implication.
We have that there exists a function
such that
.
Take an element
, then
. Now, write
and notice that
. Also, with this we have that
.
So, for every element
we have found that an element
(recall that
) such that
, which is equivalent to the fact that
is surjective. Therefore, the prove is complete.
Answer:
The first term of the sequence is -120.
Step-by-step explanation:
The formula for the "nth" term of a geometric sequence is shown below:
an = a0*r^(n-1)
Where an is the nth term, r is the ratio and n is the position of the term on the sequence. For this problem we want to find what is the initial term, a0, so we will isolate it in the formula as shown below:
a0*r^(n-1) = an
a0 = an/[r^(n-1)]
We then apply the data given to us
a0 = 31.45728/[-0.8^(7-1)]
a0 = 31.45728/[-0.8^6] =31.45728 /-0.262144= -120
The first term of the sequence is -120.
Answer:
Step-by-step explanation:
(-11) + 3
<u>-</u><u>8</u>