Subtraction of Algebraic Expressions Video Lecture | Mathematics (Maths) Class 7 (Old NCERT)

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the way we learned addition of algebraic
expressions in a similar way we will now
do subtraction with algebraic
expressions so the concept here will
remain the same so let us take one
example so let us take the first example
where we see that you have one
expression Penix
and you have another expression 1 by 2 X
and let's see that we have to subtract 1
by 2 X from 10x that means this is what
we are supposed to do so how do we do
this so are these two terms like terms
yes both of them have the same algebraic
factor so what we do we just subtract
the numerical factors that is 10 minus 1
by 2 X so this is 19 by 2 X so this is
our answer so you're also you do exactly
the same thing just that instead of
adding the numeric factors you subtract
the numeric factors that that's the only
difference let's let's look at a few
more examples so for example 2 let's say
you have one expression 3x plus 2 and
you have to subtract -2 X minus 3 from
3x plus 2 so what we do first of all we
rearrange the terms so now when you open
the bracket minus into minus becomes
plus 2 X again minus into minus becomes
plus 3 now let's collect the like terms
together 3x and 2x are like terms so
let's place them together and 2 & 3 are
like terms and let's place them together
so 3x plus 2x would be 3 plus 2x
similarly 3 plus 2 would be fine so 3
plus 2 is 5 so 5 X plus 5 so this would
be the difference between the two given
expressions let us take one more example
so before that let's quickly recap the
rules rearrange the terms collect the
light
together and then subtract the like
terms how do you subtract the like terms
just find out the difference of the
numerical coefficients of the two terms
so let's look at example three so you
have y squared plus y plus one minus y
squared plus Z so the first step is to
rearrange the terms so let's open the
brackets to Y square plus one minus y
squared minus Z select please all the
value square together so Y square minus
y square together plus y minus Z plus 1
so y square minus y square would be 0 so
you will be left with Y minus Z plus 1
so this would be the difference
so with this simple rules let us try to
subtract let us try to do some
subtraction a minus B from a plus B that
means a plus B is given and from this
you need to subtract a minus B so remove
the brackets so what do you get minus a
plus B so whenever you have a minus sign
outside the bracket the moment you
remove brackets the signs get reversed
so now let's place the like terms
together so a minus a plus B plus B so a
minus able to be 0 B plus B would be 2 B
therefore 2 B would be the answer let's
look at the next one minus M square plus
5 MN from 4 M square minus 3 MN plus 8
so for M square minus 3 MN plus 8 so
from this we need to subtract minus M
square plus 5 m in so again the first
step is rearrangement let's first remove
the brackets so you get plus M square
minus 5 m
now let's place all the M Squared
together so for M square plus M square
then minus 3m n minus 5 MN plus 8 so for
M square plus 1 M square that would be 5
M square now here you have 3 MN 5 MN or
both of them carry a negative sign so
how do we add 2 individuals with
negative sign we actually add them and
give a minus sign before them so 3 plus
5 would be 8 so this would be 8 M n with
a minus sign plus 8 so v square minus 8
MN plus 8 would be the answer thank you
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