When you need to find the distance between a point and a line there are two ways to look at it. First of all the easy approach is to plug it in to see if the point lies on the line. The second approach is to use a formula
so a student sent me this question
online and I actually went to my live
stream and started exploring it but the
problem was guess what I graphed it
wrong so everything I did on that live
stream was completely incorrect because
I don't know on the live stream I just
had a mental fart in my brain and I was
like man I got to go ahead and correct
this I got to go ahead and fix the
mistake and show you what I should have
if I had a little of time and I wasn't
on a live stream how I should have
approached the problem so as I already
previously showed we have a an equation
of a line Y = 1 6X what was it plus 6
and we want to be able to determine does
this point how far is the point from the
line so I went to go and graph it but
actually I did a slope of six over one
instead of one over six that was my
mistake guys it happens even to somebody
that's done thousands of math problems
you're capable of doing those things and
just like when you take a test sometimes
when I have a live stream like I'm not
thinking clearly right there's people
that are watching everything that I do
and it messes with my brain so I get it
when you take a test and you have this
anxiety and it's like all the
stressors breathe slow down and let's go
ahead and think about this the first
thing I always want to be able to do
especially on an equation like this
which I should have done first is well
let's just go and double check to make
sure that this point does not lie on the
line because to do the work to be
identify the distance from this point to
the line is a little bit of work and so
what I should have done first is say
well this is an X and a y coordinate can
I plug this point into this equation and
if that makes it true then that means
that point lies on the line
so I replaced a y with five and my x
with A6 I don't know why I put the one
over six in parentheses I didn't really
need to do that but it it is what it is
so 1 over 6 * -6 is just going to be a
negative
1 so in this problem guess what guys the
distance from that point to your
equation is zero look how quickly I was
able to do that that's what I should
have just gave the student the answer on
and it would have been real quick it
would have been real fast but I didn't
even think about that on my live stream
now the student might have still been
confused oh so anyway the distance is
going to be zero since it lies on the
line but Al sometimes students they
might have been asked this question and
maybe they chose the wrong one because
they wanted me to actually go through
the process of how do you find the
distance from a line to a point well
there's actually a formula for that and
a process so how about we change up the
problem real quick so for those of you
that are curious on how to do a problem
like this why don't we just change up
the numbers to the point a little bit
and so therefore we can identify what
that did distance is going to be now the
important thing is when we are doing
when we're trying to identify the
distance from a an equation to a point
we don't want to use our slope intercept
form which we're going to want to use is
going to be using a standard form of the
r
line so therefore what I simply need to
do in this case is I need to go ahead
and get all these values over to the
same side to identify my a b m my C
now it's very important that you notice
that these are capital letters and what
that means is we want these to be
integers not fractions so therefore to
get this one over six to not be a six
anymore I'm going to need to multiply
everything times a positive 6 now I'll
have a final equation of a 6 Yus a xus a
36 is equal to a zero so therefore if we
just go ahead and label this my a is
going to be a negative 1 my b is going
to equal a POS 6 and my C is equal to a
- 36 now the next piece of information
is I need to identify these points but
we're not going to use X and Y what
we're going to use for this formula is
just p and Q so p is equal to a -6 and Q
is equal to a pos4 so now once I've
identified my abc from the standard form
make sure it's in that form right don't
use this you got to use that and I've
identified my PQ which is the point that
I want to find the distance from now all
we're simply going to do is plug it into
the formula which I do not memorized but
I will write out for
you H see told you didn't have a
memorized okay so now all we're going to
do is just plug chug and simplify I'm
run out of a little space so I'll try to
do my best so we have a which is -1 * P
which is a -6 now again notice this is
an absolute value so I am going to be
using parenthesis for everything I plug
in that's going to be plus a b which is
going to be a 6 * my Q which is
4 plus a c which in this case is going
to be a
-36 and the absolute value and then I
have the square root of an a squ which
is a -1 qu^ 2 plus a b^2 qu^ s which is
going to be a 6 squ okay so let's go
ahead and write out the values up top
just because I'm running out of a little
bit of space I can find the right there
we go- 1 * 6 is going to be a POS 6 6 *
4 is going to be a 20 24 and therefore a
- 36 is just going to be a 36 so if I go
ahead and combine all of those up well 6
+ 24 is going to be a 30 30 minus 36 is
going to be -6 but remember ladies and
gentlemen it's absolute value so
distance equals absolute value of a -6
is going to be a positive 6 and then
over here I have a - 1 s which is 1 a 6
s which is 36 36 + 1 is going to be a 37
but that's under the radical so
therefore my final answer is a 6 over
the squ root of a 37 hope that helps