Question

Simplify (-2 x - 9)(-4)can someone help me...No straight answers please...

Answer 1

You just have to distribute the multiplication to each term
\[(a + b)(c) = ac + bc\]

Answer 2

Okay....

Answer 3

why adding?

Answer 4

Why not?

Answer 5

isnt it multiplying? (-2*-9)

Answer 6

So in your case you have (-2x -9)(-4) which is the same as
(-2x + (-9))(-4)

Answer 7

Oh, is that x for multiplication? or is it an x.

Answer 8

i think its multiplying... idk

Answer 9

i think it is just an x

Answer 10

ohh ok

Answer 11

So did that make sense with what you need to do Artist, or do you need a bit more help?

Answer 12

I'm not sure....

Answer 13

Ok lets try this. When you multiply a sum (a + b + c+ ...) by a number k. You simply multiply each of the terms in the sum by that same number k.

Answer 14

So in your case, what is the sum you're multiplying ?

Answer 15

(-2 x - 9)(-4)

Answer 16

Not quite.

(-2x - 9) is a sum.

Answer 17

Specifically it is the sum of -2x and -9

Answer 18

Okay

Answer 19

You know what a sum is right?

Answer 20

Yes...

Answer 21

Tell me =)

Answer 22

One of the most important things to learn in math is the vocabulary. Otherwise it is very difficult to understand what we are talking about if we aren't using the same words for things.

Answer 23

Okay.

Answer 24

What is a sum?

Answer 25

A sum is the answer of two numbers added together...

Answer 26

Close. Actually a sum is a sequence of terms added together.

2 is not a sum.
2 + 3 is a sum.
2*5 is not a sum.
2+3 + 2*5 is a sum.

Answer 27

Oh...Okay.

Answer 28

Now then. For each of the sums I listed above, count the number of terms in each sum.

Answer 29

2, then 4?

Answer 30

Close. But notice that the 2 is not being added to the 5, it's multiplied. The terms of a sum are _ONLY_ the things being added together.

Answer 31

So how many terms does that last sum have?

Answer 32

*Lightbulb*...Okay...

Answer 33

3?

Answer 34

I am glad I fanned you btw. You've been the best student I've seen here in a long time.

Answer 35

Yes, it has 3.

Answer 36

Really?

Answer 37

Yes.

Answer 38

I'm the best?

Answer 39

So far ;)

Answer 40

Cool...

Answer 41

Ok so now. Going back to what I was saying before.. If you have a number k multiplied by a sum. You simply distribute the multiplication of k to each term in the sum.

Answer 42

okay...

Answer 43

So lets look at your problem again.

Answer 44

(-2x - 9)(-4)
What is the sum, and what is k?

Answer 45

the sum is (-2x-9)?

Answer 46

Yes!. But I get confused easily, so can you rewrite that as an equivalent sum (equals the same thing) so that it is explicitly two terms being _ADDED_ together?

Answer 47

Can you rewrite subtraction as adding a negative?

Answer 48

no...?

Answer 49

2-9 = 2+(-9)
-7 = -7
Right?

Answer 50

Yes.

Answer 51

So do the same thing to the subtraction you have in your sum

Answer 52

I like my sums to only have addition.

Answer 53

feels neater ;p

Answer 54

Yeah...

Answer 55

so, -2x + (- 9,) ?

Answer 56

Yes.

Answer 57

So now you have this sum (-2x + -9) and you're
multiplying it by (-4). So to do that you just multiply
each term in the sum by the -4.

(a + b)(c) = a*c + b*c

Answer 58

So what do you get?

Answer 59

-4*-2+ -4*-9?

Answer 60

Close. Don't forget your x.

Answer 61

8x + 36

Answer 62

like that?

Answer 63

Yes, exactly.

Answer 64

:)

Answer 65

Nice work!

Answer 66

Thank you!