Like Foil, the double distributive method is used for multiplying 2 binomials.

How "double" distributive works

Unlike "single" distribution which only distributes 1 single term , double distribution requires two terms (a binomial) to distribute over a second binomial .

So, in this example, you have to distribute that first x and also that 5 over the second binomial .

Step 1

Distribute out both terms

Step 2

Simplify like terms

$
-3x -21 + x^2 + 7x
\\
x^2 + 4x - 21
$

Step 1

Distribute out both terms

Step 2

Simplify like terms

$
-3x -9 + x^2 + 3x
\\
x^2 \red{-3x + 3x} -9
\\
x^2 -9
$

Step 1

Distribute out both terms

Step 2

Simplify like terms

$
-4x -12 + 2x^2 + 6x
\\
2x^2 +2x - 12
$

Step 1

Distribute out both terms

Step 2

Simplify like terms

$
-24x +8 + 3x^2 -x
\\
x^2 -25x +8
$