Name: ファクタリングを完全に実行した例 (Worked examples factoring completely)
Uploaded: 2021-01-14T10:14:20.000Z
Duration: 4 min
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

法助動詞 A2

- [Instructor] So let's see if we can try to factor

命令形

All right, now let's work through this together.

So the way that I like to think about it,

I first try to see is there any common factor

to all the terms, and I try to find the greatest

possible common factors to all of the terms.

So let's see, they're all divisible by two,

but let's see, they're also all divisible by four,

four is divisible by four, eight is divisible by four,

and that looks like the greatest common factor.

Well if I factor a four out of four x squared,

I'm just going to be left with an x squared.

If I factor a four out of negative eight x,

negative eight x divided by four is negative two,

And if I factor a four out of negative 12,

negative 12 divided by four is negative three.

Well it looks like I could factor this thing

Can I think of two numbers that add up to negative two,

and when I multiply it I get negative three,

since when I multiply I get a negative value,

A times B needs to be equal to negative three.

So let's see, A could be equal to negative three

because negative three plus one is negative two,

and negative three times one is negative three.

or I could just write that as x minus three,

And now I have actually factored this completely.

negative three x squared plus 21 x minus 30.

Pause the video and see if you can factor this completely.

So what would be the greatest common factor?

So let's see, they're all divisible by three,

Let's see what happens if you factor out a three.

21 x divided by three is seven x, so plus seven x,

and then negative 30 divided by three is negative 10.

but having this negative out on the x squared term

So instead of just factoring out a three,

If we factor out a negative three, what does that become?

Well then if you factor out a negative three out

of this term, you're just left with an x squared.

If you factor out a negative three from this term,

21 divided by negative three is negative seven x.

And if you factor out a negative three out of negative 30,

you're left with a positive 10, positive 10.

And now let's see if we can factor this thing

Can I think of two numbers where if I were to add them

and if I were to multiply them, I get to 10?

And let's see, they'd have to have the same sign

So let's see A could be equal to negative five,

So I can re-write this whole thing as equal

to negative three times x plus negative five,

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ファクタリングを完全に実行した例 (Worked examples factoring completely)

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expression

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