Maths Simple Equation part 2 (Constant, Variables, Expression) CBSE Class 7 Mathematics VII Video Lecture

hello friends this video on simple
equations part 2 is brought to you by
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before we talk more about equation let
us have a quick recap on constants and
variables I am sure that you all know
what are they but still we will have a
quick recap
so constants are those values which have
a fixed value of their own so these are
basically the numbers so for example you
talk about numbers like 550 162 3540 2
now each of these are numbers and when
you say numbers they always have your
own band if I say fine if I say 5 rupees
5 rupees means 5 rupees 5 can never
become equal to 10 five can never become
equal to 1 by 5 your five can never
become equal to minus five so all of
these are constants whether you talk
about fractions or you talk about the
negative numbers or you talk about the
decimal numbers these are all examples
of constants so constants means they
will always have the same value that is
why they have a fixed value so here why
do you see this picture so this picture
is to show that four constants itself
they will always have the same haircut
or the same hairstyle so the hairstyle
is normally change evers that's a
constant hairstyle or a fixed hairstyle
and these are constants when you talk
about variables they have changing
values so they can take different values
let me give you an example now let us
talk about any numbers not number
because numbers always have fixed values
let's talk about the variable X there
generally these variables are denoted by
alphabets like XYZ ABC PQ rmn etc so
they are always denoted by alphabets and
these alphabets they can take different
values depending upon the situation so
their values keep on changing just like
this girl you see right now she has
brown hair
now then she goes to a fancy dress
competition
she puts a week she colors her hair and
now she has got away viewed hair color
she has a dreamy share color because
she's going to a fancy dress competition
again the same person when she is again
going to a funky party she has a very
short hair and that to the hair is like
blonde sometime else when she wants a
very different look she might even have
spikes like this so the person is the
same the hair is the same it is just
that the hairstyle and the hair color is
changing depending upon the ambience
where she is going
when she is going to a party she is
having a funky hair style when she is
going to a fancy dress competition she's
having a very different hairstyle when
she is going to maybe a cool place with
maybe a family outing with her families
and friends then she's having spikes
when she's going to school she is having
when she's going to school she's having
the regular haircut so variables are
like that depending up on the situations
their values changes let me give you an
example of a variable let's talk about
eggs now what is the value of x because
x as such is an alphabet so it's when I
see value of X it has to be some number
so can you see that the value of x is
all is 1 you can't say that let me give
you examples let us take examples of
different equations with X let's say we
have one equation X minus 2 is equal to
6 let's see if we have another equation
12 minus X is equal to 6 let's see we
have yet another equation 3x is equal to
12 now when you find out the value of x
in this equation now finding value of x
means you have to put such a value of x
so that this relationship should hold
true that means X minus 2 should be
equal to 6 so in this case you find that
the value of x is 8 so if you put 8
instead of X 8 minus 2 is 6 so here in
this equation
X is equal to eight similarly when you
find the value of x in this equation you
see that the value of x here is six when
you put X is equal to six 12 minus six
is six in the third equation the value
of x is 4 when you put X is equal to
four three into four is 12 so X is equal
to four so what is happening if you see
that the same variable X is taking
different values 8 6 & 4 in different
equations this the same way this girl
was taking different hairstyles in
different parties in a fun party it was
different in school it was different in
again in a family party it was different
similarly the values of that that X is
acquired in is different depending upon
the city so X is a variable so these are
variables now many times children get
confused between expressions and
equations so let us very neatly
distinguish the two now when we talk
about a mathematical expression so
expression is all about a phrase with
numbers variables and operators so you
will have constants you will have
variables you will also have operators
like + - / Takai so you will have all
these operators but you will not have an
equality sign so you aren't basically
not equating anything in an expression
so examples of expression would be 3x +
4 this is an expression y + 15 is also
an expression 20 B this is an expression
you have constants variables 30 divided
by a plus B so this is also an
expression so these are all examples of
expression so in an expression you
really do not have an equality sign so
there is no equality sign involved in an
expression but when we talk about an
equation equation definitely has an
equality sign because it is a statement
of equality between two expressions so
something of this sort 3x plus 4 the
same expression when it gets equated to
something
else then it is called an equation so
now three eighths plus four is this part
is still an expression but overall this
entire thing is an equation similarly 30
divided by a plus B is equal to 12 this
thing overall is an equation 20 B is
equal to y plus 50 so you see in the
previous example we saw this is an
expression this is an expression but
when we equate the two of them with an
equality sign it becomes an equation and
in any equation do you know what is the
purpose of this equality sign this
equality sign tells us that whatever we
have on the left hand side is equal to
whatever we have on the right hand side
so basically this tells us that LHS has
to be equal to RHS now that means for
example here the value of x should be
such that 3 into X plus 4 should be
equal to 0 so this is a mandatory
criteria that anything on left hand side
has to be equal to anything on right
hand side so primarily this is the
difference between an expression and an
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