Question 885580
By Pythagoras theorem

(x-1)^2+(2x)^2=(2x+1)^2

x^2-2x+1 +4x^2=4x^2+4x+1

x^2-6x=0

x(x-6)=0

x=0 OR 6



length of ladder = 6*2 = 12 feet