Can I express $x^7y+xy+x+1$ by a repeated use of operation $xy+x+y+1$? A certain calculator can only give the result of $xy+x+y+1$ for any two real numbers $x$ and $y$. 
How to use this calculator to calculate $x^7y+xy+x+1$ for any given $x$ and $y$?  
When $x$ and $y$ are equal, it will give $(x+1)^2$. But I cannot proceed beyond that. 

Give $x^7$ and $y$ to the calculator, to get $R_1 = x^7y + x^7+y +1$.
Give $x$ and $y$ to the calculator, to get $R_2 = xy+x+y+1$.
Add $R_1$ and $R_2$ to get, $R = R_1+R_2 = x^7y + x^7 + x+xy + 2y+1$.
Subtract $x^7$ and $2y$ from $R$ to get the required.
