a) Ta có: \(x^2+10x+26+y^2+2y=\left(x^2+10x+25\right)+\left(y^2+2y+1\right)\)

\(=\left(x+5\right)^2+\left(y+1\right)^2\)

b) Ta có: \(a^2+5b^2+2ab+4b+1=\left(a^2+2ab+b^2\right)+\left(4b^2+4b+1\right)\)

\(=\left(a+b\right)^2+\left(2b+1\right)^2\)

c) Ta có: \(4x^2+4x+10+6y+y^2=\left(4x^2+4x+1\right)+\left(y^2+6y+9\right)\)

\(=\left(2x+1\right)^2+\left(y+3\right)^2\)