1.) x2+y2=45,xy=18,then 1/x+1/y=? 2.)when a square is constructed on 3 sides of a triangle ,their sides are in the ratio 1:3:4,THE WAT triangle is...

We'll solve just the 1st problem since you have to ask
only one question.

To determine the sum of the fractions
we'll have to determine the least comon denominator, which is
xy.

1/x + 1/y = (y+x)/xy

We
already know the value of xy, which is 18. We'll calculate the value of x +
y.

For this reason, we'll have to create a perfect square
to the left side:

(x^2 + y^2 + 2xy) - 2xy =
45

(x+y)^2 = 45 + 2xy

x + y
=`+-` `sqrt(45+2*18)`

x + y =`+-`
`sqrt(81)`

x+  y = `+-` 9

Now,
we'll calculate the requested sum:

1/x + 1/y =
(y+x)/xy

Let x+y=9 => (y+x)/xy = 9/18 =
1/2

Let x+y=-9 => (y+x)/xy = -9/18 =
-1/2

The requested values of the sum 1/x +
1/y are {-1/2 ; 1/2}.