Multiplying binomials help please?

example:

(ax + by) (cx + dy)

FOIL is First, Outer, Inner, and Last.

the first terms are ax and cx, so when we multiply, acx^2

the outer terms are ax and dy, so, axdy

the inner terms are by and cx, so bcxy

the last terms are by and dy, so bdy^2

therefore the answer for this one is acx^2 + axdy + bcxy + bdy^2

let's take this as an example:

(5x+3)(3x-7)

Using FOIL,

First = (5x)(3x)

Outer= (5x)(-7)

Inner= (3)(3x)

Last= (3)(-7)

When we add them, 15x^2 - 35x + 9x - 21

Finally, 15x^2 - 26x - 21.

I hope I was able to help.

(3x - 2)(4x + 7) =

FIRST 12x^2 (multiply 3x times 4x)

OUTSIDE + 21x (multiply +7 times 3x)

INSIDE - 8x (multiply the -2 times 4x)

LAST -14 (multiply the -2 times 7) =

(add common terms) 12x^2 + 21x - 8x - 14 =

12x^2 +13x - 14

The -2 let's you know to subtract. All the other terms are positive. If you have multiply two terms with - in front, then minus times minus is plus.

Example:

(-x +1)( -2x -3)

F: -x*-2x = +2x^2

O: -x*-3 = +3x

I: 1*-2x = -2x

L: 1*-3 = -3

2x^2 +3x -2x -3 (combine like terms) =

2x^2 +x -3

Disitributive is basically foil

example: (x-4)(x+1)

First term: x*x=x^2

Second: 1*x=x

Third: -4*x=-4x since there is a negative in front of the 4, the term is negative

Final: -4*1=-4

Your answer would be x^2-3x-4

I hope this helps...

Example: (x-4)(x+3)

F (x)(x) = x^2

O (x)(3) = 3x

I (-4)(x) = -4x

L (-4)(3) = -12

x^2 + 3x -4x -12

Simplify to x^2 -x -12

Is there a specific part of that that confuses you?

when u foil if the number u get is negative, subtract it

when its positive add it

also:

(a+b)(a+b)=a^2 +2ab+b^2

(a-b)(a+b)=a^2-b^2

(a-b)(a-b)=a^2-2ab-b^2