Cambridge University Admission Interview Tricks | Find x+y=?

[@raghvendrasingh1289]

Let x+y = t
then x - y = 40/t
we know that
(x+y)^2 - (x - y)^2 = 4 xy
t^2 - 1600/(t^2) = 396
t^4 - 396t^2 - 1600 = 0
(t^2 - 400)(t^2+4) = 0
t = 20 , -20 , 2 i , -2 i

[@hariomdas270]

X^2-Y^2=40
X
(X-Y)(X+Y) =40
40=2*20,4*10,5*8,
(1)2*20
X-Y=2,----------(1)
X+Y=20--------(2)
ADD(1)+(2)
2X=22
X=11
EQUETION (1) MINUS EQ(2)
X+Y-X+Y=20-2
2Y=18
Y=9
ANSWER
X=11
Y=9
X^2-Y^2=11^2-9^2=121-81=40
X.Y=11*9=99

[@hafeezrehman8692]

Value of X and Y?

[@9허공]

problem is x + y not (x, y)

[@Radioayandeh]

No need to calculation, x=11 & y=9