factor
x squared+ 8x+3
x^2+8x+3
64-12=52/4=13
(x+4-sqrt13)(x+4+sqrt13)
checking,
x^2+4x+x*sqrt13+4x+4sqrt13+16-xsqrt13-4sqrt13-13
x^2 +x(+sqrt13+8-sqrt13)+16-13=
x^2+8x+3
x squared+ 8x+3
64-12=52/4=13
(x+4-sqrt13)(x+4+sqrt13)
checking,
x^2+4x+x*sqrt13+4x+4sqrt13+16-xsqrt13-4sqrt13-13
x^2 +x(+sqrt13+8-sqrt13)+16-13=
x^2+8x+3