#### Answer

$1-2r+r^2$

#### Work Step by Step

We start with the given expression: $(1-r)^2$
To simplify an algebraic expression, we must eliminate any parentheses and combine like terms.
We expand the squared term:$(1-r)(1-r)$
We apply the distributive property to multiply the binomials: $1-r-r+r^2$
We combine the like terms by subtracting: $1-2r+r^2$