FOIL help

[-Setro-]

more like foil hell
yeah so im confused about foil on one little thing because our math teacher is terrible and only gives like 2 examples, not including some subtraction
so heres the problem:
(4x - 9) (3x + 1) = ?
When doing the I part of foil, is the 9 negative because of the minus sign behind it, or is it just a 9?
Sorry about so many questions, my math teacher yelled at someone for saying they didnt understand something before...

[Ad Bot]

[Katadeus]

It's a negative nine
Treat it like (A + B)(C + D)
In this case it would be (4x + -9)(3x + 1)

[-Setro-]

Ah, thanks.
Another thing, what is 2x times 2y?
4xy?
4x^2y^2?

[Col. Burton]

(4x - 9) (3x + 1) = ?

First
Outer
Inner
Last

4x X 3x = 12x^2
4x X 1 = 4x
-9 X 3x = -27x
-9 X 1 = -9
12x^2 + 4x - 27x - 9

what is 2x times 2y?
4xy?
4x^2y^2?

I don't think you can multiply 2 numbers with different variables. then again idk what kind of math you are doing.

[Ipquarx]

I don't think you can multiply 2 numbers with different variables. then again idk what kind of math you are doing.

(2*x)*(2*y) = 2*x*2*y = 4*x*y = 4xy

[Zanaran2]

2x * 2y is 4xy.
Think of it as 2*2 * x*y.

Also I'm late on this but when you are trying to determine if a number is negative or positive, the minus or positive sign behind it will usually determine it (don't worry about * or /, they usually aren't present in algebra)

for example 5 - 9 can be read as 5 + -9

[Col. Burton]

(2*x)*(2*y) = 2*x*2*y = 4*x*y = 4xy

I understand now, you just can't add numbers with different variables. If it was 2x + 2y, it wouldn't be able to be added together. I always get confused about that.

Yes, the answer would be 4xy. You CANNOT, however, add them. If the problem was 2x+4y than you can't combine.

[ßlöükfáce]

12x^2 + 4x - 27x - 9

then you can simplify to 12x^2 - 23x - 9, because of the like terms rule

[Col. Burton]

then you can simplify to 12x^2 - 23x - 9, because of the like terms rule

True, I absolutely love algebra, idk why.

[A million souls]

You can always express it like this:
4x (3x + 1) + -9 (3x +1)

[Headcrab Zombie]

You can always express it like this:
4x (3x + 1) + -9 (3x +1)

But why
that's not simplified

[Satan From Wreck-It-Ralph]

You can always express it like this:
4x (3x + 1) + -9 (3x +1)

what the forget
I know almost nothing about FOIL and I know that's wrong.

[the hacker]

Does this help?

[Zack]

Does this help?

I was thinking of doing this...

but now my plans are FOILED...

[Tayasaurus]

Does this help?

No but you can use it to mask your TERRIBLE HUMOR