(r - s)^2 - t^2
USE FORMULA a^2 - b^2 = (a+b) ( a-b)
( r -s + t) ( r-s -t ) ANSWER
r^2-rs-sr+s^2-t^2
Comments
USE FORMULA a^2 - b^2 = (a+b) ( a-b)
( r -s + t) ( r-s -t ) ANSWER
r^2-rs-sr+s^2-t^2