Hello, i am experiencing all kinds of confusion as far as FOIL goes. I understand the concept, and I got the first bunch of questions right aka
(x - 7) (x + 10)
x^2 + 10x - 7X + 70
x^2 + 3x + 70
but then I am encountering ones like (3r + 9) (2r - 1) and i did
(3r + 9) (2r - 1)
6r^2 + 3r - 18r - 1
6r^2 + -15r - 1
... but the answer says 6r^2 + 15r - 1 (without the negative). Wouldn't it have to be 18r - 3r to be a non-negative 15? Also I am confused as to when to put a plus sign and when to put a minus sign. We are also doing solving linear equations and when I am attempting to balance the sides, I am just randomly choosing a plus or a minus sign sometimes to be honest. Because I just have no idea.
Also, a lot of the advance questions on this sheet... I have no idea how to attempt. Such as these ones (instructions say Expand and simplify)
(a - 4) (a - 6) + 5(3a - 2) [What do I do with the second part.. with the 5?]
(x + 5)(x - 3) + (x - 4)(x + 2) [Do I do the one side and then the other and then simplify them together?]
And this one here (the instructions above say Simplify by first expanding binomials)
4(x + 6)(x - 4) [I really just have no idea on this one... what do i do with that 4?]
Sorry that this is a bit long. I'm just really confused.
(x - 7) (x + 10)
x^2 + 10x - 7X + 70
x^2 + 3x + 70
but then I am encountering ones like (3r + 9) (2r - 1) and i did
(3r + 9) (2r - 1)
6r^2 + 3r - 18r - 1
6r^2 + -15r - 1
... but the answer says 6r^2 + 15r - 1 (without the negative). Wouldn't it have to be 18r - 3r to be a non-negative 15? Also I am confused as to when to put a plus sign and when to put a minus sign. We are also doing solving linear equations and when I am attempting to balance the sides, I am just randomly choosing a plus or a minus sign sometimes to be honest. Because I just have no idea.
Also, a lot of the advance questions on this sheet... I have no idea how to attempt. Such as these ones (instructions say Expand and simplify)
(a - 4) (a - 6) + 5(3a - 2) [What do I do with the second part.. with the 5?]
(x + 5)(x - 3) + (x - 4)(x + 2) [Do I do the one side and then the other and then simplify them together?]
And this one here (the instructions above say Simplify by first expanding binomials)
4(x + 6)(x - 4) [I really just have no idea on this one... what do i do with that 4?]
Sorry that this is a bit long. I'm just really confused.