Find the area of the following:
-square whose sides are (x+1) in length

Area of Square = Base*Height 
Base=(x+1) Height=(x+1)
Therefore Area=(x+1)(x+1) or (x+1)^2
By expanding the brackets e.g. x*x is x^2 then x*1 is x and so on you get:
x^2+x+x+1 this simplfies to x^2+2x+1
Area = x^2=2x+1
Unless they have given you a value for x, this is the equation for the area of said square.