Question

(r-1)^2 this is to the power of two

Answer 1

(r-1)^2= (r-1)(r-1)

Foil:

First: r*r=r^2
Outer: r*-1= -r
Inner: r*-1= -r
Last: -1*-1= 1

Put it together and simplify:
r^2-r-r+1
r^2-2r+1

Final answer: r^2-2r+1

Answer 2

Use formula: (a-b)² = a² - 2ab + b²

(r-1)² = r² - 2r + 1