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# Writing algebraic expressions example 2

Video transcript

First, consider the
expression for take the quantity of negative
4 times x and add 9. So let's see,
we're going to take the quantity of
negative 4 times x. Well, negative 4 times x is
just going to be negative 4x. And then they say--
so we're going to take that quantity, that's
this thing right over here, and then they say add 9. So let's add 9 to it, so
that's this first sentence. Take the quantity of
negative 4 times x and add 9. That's this expression
right over here. Now select the
answer that matches the following-- the sum of 4
and the product of negative 9 and that expression. So let's think about this. The sum of 4, so
we're going to take 4 and we're going to add it to the
product-- we're going to add it to-- I'm running out of colors. Maybe I will do this
in this-- let' see. I've already used blue and
I've already used orange. I'll use green. So we're going to take
that 4, the sum of 4 and the product of negative
9 and that expression. So we're going to add 4
to the product-- we're going to multiply negative 9
times this expression right up here. So it's negative 9
times negative 4x, negative 4x plus 9. Now let's see if any
of these actually match what I just
wrote right over here. So let's see, this one is 4. Here we're taking a 4
and we're multiplying it times negative
4x minus 9, and then we're subtracting that, so
this seems very different, so I'll scratch that one out. Let's see. This has positive 9 times
negative 4x plus 9 plus 4, so this is very close,
but this says positive 9, this says negative 9, so
I'll cross out one out. This one has 4 times 9x plus 4. Well, no, we have
negative 4x plus 9, this is different
in multiple ways, and they're multiplying it
by 4 instead of negative 9. This one, let's see, we have
a negative 9 being multiplied by negative 4x plus 9,
and then we are adding 4. So all you have to do to
go from this expression to this expression, instead
of adding the 4 there, you just add the 4
here, and then these two are identical expressions. So we will go with this
one right over here.