Question

write f(x) = x2 + 8x + 3 in vertex form

Answer 1

vertex is at \(x=-\frac{b}{2a}=-\frac{8}{2}=-4\)

Answer 2

so vertex form will be
\[y=(x+4)^2+\text{something}\] and you find the something by replacing x by -4 in the original expression to see what you get

Answer 3

you could also complete the square