How to find the intersection point of two linear equations

Brian McLogan
1.3K followers
Oct 31, 2024
http://www.freemathvideos.com In this video series I show you how to solve a system of equations by graphing. When solving a system of equations by graphing we graph each equation separately and then analyze where the two lines intersect or if at all. If the two lines intersect at a point then the values of the x and y coordinates are our solution of the system. If our graphs are the same line then we have infinite many solutions and if the graphs are parallel and never intersect then we have no solution.
x + y = 3 , 3x - 2y = 4
okay um if i was gonna be solving a
problem like this
what it wants us to do is it wants us to
find the intersection of the two points
so
what we're gonna need to do is see when
will these two equations you know equal
each other when will they cross so what
we'll look at is you know if we said
something like this
okay
where are their points going to be
exactly the same so if you think of this
here's your y and here's your x right so
what i'm saying is at this intersection
point the x value
and the y value are going to equal each
other for both the um for both equations
so what i'm saying is what we're going
to do is we have two different equations
we want to find when does the x value
equal the y value
so
mrs garvin would you please come to the
main office mrs garvin please come to
the main office and not go to r9 portal
r9
also officer smith would you please come
to the conference room would you please
come to the principal's conference room
officer smith
okay um so then to go and figure this
out what we're going to have to do
video yeah
just come by and say hi
i want to see what you're doing right
now okay we're doing intersections with
two lines
will you just sit down i'll be on with
done with this video in two seconds
thank you for showing me what you're
doing um so then what we're gonna want
to do
is here
let's solve for y so if i subtract the x
on both sides
i get y equals a negative x plus three
okay
so now if i want to set these equal to
each other right
i want to say well i know that my y
values have to be the same for both of
these equations my two y values have to
be exactly the same
so therefore what i'm going to do is i'm
going to plug this equation into the
other one so i'll obtain 3x minus
2 times negative x plus 3
equals 4.
all right
then what i can do is when the y values
are the same meaning i plugged one y
value to the other one i can find when
will the x values be the same so i'll
use distributive property to give me 3x
plus a 2x negative 2 times negative x
gives you positive 2x
minus 6
equals 4. combine my like terms to give
me 5x
minus 6 equals 4
add 6
5x equals 10
divided by 5
x equals 2. so what that tells me is
when my y values are equal to each other
my x value is equal to 2.
so now the next thing i need to do is
now well if x equals 2 what is my y
value for both those problems so let's
go and
take a look at that what i can do is i
can plug 2
in for x and figure out what my y is
going to be so i'm going to plug it into
both equations so you guys can see that
when x equals 2 my y values are going to
be exactly the same and that also will
figure out what the y value is so i plug
in 2
plus y equals 3. subtract 2
y equals 1.
and we'll say that value is 1.
or you could have plugged it in this
equation 3 times two minus two y
equals four three times two is
six minus two y
equals four
subtract six
negative two y equals a negative two
divided by negative 2
y equals 1. so again remember when
you're dealing with intersection you
want to set your equations equal to each
other plug one equation in for the other
so y equals x minus 3. so therefore i'm
going to plug that in solve for my one
variable x then once i know the value of
x where the two equations meet i can
plug that into either one of the
equations and i'll find the y value for
when the two equations mean and that's
how you find the intersection of two
points
