Applicare la formula: $ax+by$$=\left(\frac{a}{mcd\left(a,b\right)}x+\frac{b}{mcd\left(a,b\right)}y\right)mcd\left(a,b\right)$, dove $a=-104$, $b=-169$, $ax+by=16-104x^2-169x^4$, $ax=-104x^2$, $by=-169x^4$, $x=x^2$ e $y=x^4$

Applicare la formula: $x\left(a+b\right)$$=xa+xb$, dove $a=x^2$, $b=\frac{13}{8}x^4$, $x=-13$ e $a+b=x^2+\frac{13}{8}x^4$