Theory:

To subtract polynomials, first reverse the sign of each term we are subtracting (in other words turn "\(+\)" into "\(-\)", and "\(-\)" into "\(+\)"), then add as usual.
Example:
Subtract p(x)=5+x2x2 and  q(x)=3x²6x4.
 
=2x² +x+5(3x²6x4)
 
Now change the sign of \(q(x)\).
 
\(= -2x^2 + x +5-3x^2 +6x +4\)
 
=2x²3x²+x+6x+5+4
 
=23x²+1+6x+5+4
 
=5x² +7x+9