<s>[INST] If $abcd=1$,where $a,b,c,d$ are positive reals,then find the minimum value of $a^2+b^2+c^2+d^2+ab+ac+ad+bc+bd+cd$. If $abcd=1$,where $a,b,c,d$ are positive reals,then find the minimum value of $a^2+b^2+c^2+d^2+ab+ac+ad+bc+bd+cd$.

Let $E=a^2+b^2+c^2+d^2+ab+ac+ad+bc+bd+cd=(a+b+c+d)^2-(ab+ac+ad+bc+bd+cd)$
I do not know how to use $abcd=1$ in this question to get the minimum value of the expression. 
 [/INST] HINT
Use the AM-GM inequality, which establishes $$\frac{a_1+a_2+\dots+a_n}{n} \ge \sqrt[n]{a_1a_2\dots a_n}$$
When $a_1,a_2, \dots, a_n$ are positive reals. 
For example, $a^2+b^2+c^2+d^2 \ge 4\sqrt[4]{a^2b^2c^2d^2}=4$
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