Rewrite as .

Expand by multiplying each term in the first expression by each term in the second expression.

Multiply by .

Rewrite using the commutative property of multiplication.

Multiply by .

Multiply by .

Multiply by .

Rewrite using the commutative property of multiplication.

Multiply by .

Move .

Subtract from .

Reorder and .

Add and .

Move .

Subtract from .

Expand (r-t+n)^2