X²-2xy+y²+a²=(x-y)²+a².
a²b²+2+2ab=(ab)²+2ab+1²+1²=(ab+1)²+1².
x²+2x+5=x²+2x+1+4=x²+2x+1²+2²=(x+1)²+2².
x²+4xy+y²+x²y²+1=(x²+2xy+y²)+(x²y²+2xy+1)=(x+y)²+(xy+1)²
4x²+c²-4x+1=(2x)²-4x+1+c²=(2x-1)²+c².
9b²-6b+4c²+1=(3b)²-6b+1+(2c)²=(3b-1)²+(2c)².
a²+2ab+2b²+2b+1=a²+2ab+b²+b²+2b+1=(a+b)²+(b+1)².
x²+y²+2x+6y+10=x²+2x+1+y²+6y+9=(x+1)²+(y²+6y+3²)=(x+1)²+(y+3)².