Question

If $abcd=1$ where $a,b,c,d$ are positive reals then the minimum value of $a^2+b^2+c^2+d^2+ab+ac+ad+bc+bd+cd$ is

Answer 1

Answer: 10

Use $AM\ge GM$ between the given $10$ numbers i.e. $a^2,b^2,c^2,d^2,ab,ac,ad,bc,bd$, and $cd$