Question #2ce3a

1 Answer
Sep 15, 2016

((x = 1, y = 16),(x = 16, y = 1))

Explanation:

Calling a = (x/y)^(1/2) in

(x/y)^(1/2) + (y/x)^(1/2) = 17/4
x/(y^(1/2)) + y/(x^(1/2)) = 65/4

we obtain

((a+1/a=17/4),(a sqrt(x)+sqrt(y)/a=65/4))

Solving for a,x we have

((a = 4, x = 1/256 (4225 - 130 sqrt[y] + y)),(a = 1/4, x = 4225 - 2080 sqrt[y] + 256 y))

The first solution gives

a = 4 so a^2 = x/y = 16 them follows

x=16y=(4225 - 130 sqrt[y] + y)/256 or

(16 xx 256 y - y -4225)^2=(-130sqrt(y))^2 or

3969 y^2- 8194 y +4225=0

with roots {color(red)(y = 1),color(red)(x=16)} and {y = 4225/3969, x = (16 xx4225)/3969 }

The second solution gives

a = 1/4 so a^2=x/y=1/16 following

x = y/16 =4225 - 2080 sqrt[y] + 256 y or

y = 16 (4225 - 2080 sqrt[y] + 256 y) or

(y-16 xx 256 y - 16 xx 4225)^2=2080^2y or

3969 y^2 - 131104 y + 1081600=0

with roots {color(red)(y = 16), color(red)(x = 1)}and {y = 67600/3969,x =67600/(3969 xx 16)}

Ressuming, the real feasible solutions are:

((x = 1, y = 16),(x = 16, y = 1))

Attached the solutions region.

In blue

x/(y^(1/2)) + y/(x^(1/2)) = 65/4

and in red

(x/y)^(1/2) + (y/x)^(1/2) = 17/4

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