Question 670506
length =x

width = (x-10 )

diagonal = (x+10)

They form a right triangle.
Apply Pythagoras theorem

(x+10)^2=x^2+ (x-10)^2

x^+20x+100=x^2+x^2-20x+100

2x^2=40x
/x
2x=40
x= 20 the length of the TV