1. (а+4)²-2(а+4)+1=a²+8a+16-2a-8+1=a²+6a+9=(a+3)²
2. (3b+2)²+4(3b+2)+4=9b²+12b+4+12b+8+4=9b²+24b+16=(3b+4)²
3. (3y+8)²+(4у+6)²+4у=16y²+48y+36+4y=25y²+100y+100=(5y+10)²
4. (х-5у)²+(х+12у)²-х(х-12у)=x²-10xy+25y²+x²+24xy+144y²-x²+12xy=x²+26xy+169y²=(x+13y)²