Solution 1: Rewrite the given expression as (x2+4)(1+y2)+14(x+2y)+94. By Cauchy-Schwartz, this is at least (x+2y)2+14(x+2y)+94=(x+2y+7)2+45. The minimum is 45 , attained when xy=2,x+2y=−7. Solution 2: Let z=2y,s=x+z,p=xz. We seek to minimize (2xz)2+(x+7)2+(z+7)2=4p2+(x2+z2)+14(x+z)+98=4p2+s2−2p+14s+98=(2p−2)2+(s+7)2+45≥45 Equality holds when s=−7,p=4. Since s2≥4p, this system has a real solution for x and z.