Question 1066475
.
x^2 + x*(x+20) = 342.


Solve for x.


2x^2 + 20x - 342 = 0,

x^2 + 10x - 171 = 0,

(x+19)*(x-9) = 0.


The only positive solution is x = 9.


<U>Answer</U>.  The side of the square is 9 m.