Question to this algebra question?

If f(x)=3x-1 and f(a)=5, what is the value of a

2 Answers
Jun 26, 2018

#a=2#

Explanation:

If #f(x)=3x-1#
then #f(a)=3a-1#
and
since we are told #f(a)=5#
we have #3a-1=5#

#color(white)("xxxxx")rArr 3a=6#

#color(white)("xxxxx")rArr a=2#

Jun 26, 2018

#a=2#

Explanation:

#f(a)# means that there is some value #a# that when I plug it into #f(x)#, it evaluates to #5#.

In other words, we are essentially being asked what is our input, when our output is #5#?

Let's set #f(x)# equal to #5#:

#3x-1=5#

We can add #1# to both sides and dividing the result by #2# on both sides. We get

#x=2#

Another way we can write this is

#f(2)=5#

When we input #2# into our function, we get #5#. Therefore,

#a=2#

Hope this helps!