\(x^2-6x+9=x^2-2.3x+3^2=\left(x-3\right)^2\)
\(\frac{1}{4}a^2+2ab^2+4b^4=\left(\frac{1}{2}a\right)^2+2.\frac{1}{2}a.2b^2+\left(2b\right)^2=\left(\frac{1}{2}a+2b\right)^2\)
\(25+10x+x^2=5^2+2.5x+x^2=\left(5+x\right)^2\)
\(\frac{1}{9}-\frac{2}{3}y^4+y^8=\left(\frac{1}{3}\right)^2-2.\frac{1}{3}y^4+\left(y^4\right)^2=\left(\frac{1}{3}-y^4\right)^2\)
a,(x-3)^2
b,(1/4x+2b^2)^2
c,(5+x)^2
d,(1/3-y^4)^2