we have
[tex] f(x)=8x^{2} +4x [/tex]
Let
[tex] y=f(x) [/tex]
[tex] y=8x^{2} +4x [/tex]
Factor the leading coefficient
[tex] y=8(x^{2} +0.5x) [/tex]
Complete the square. Remember to balance the equation by adding the same constants to each side
[tex] y+0.5=8(x^{2} +0.5x+0.0625) [/tex]
Rewrite as perfect squares
[tex] y+0.5=8(x+0.25)^{2} [/tex]
[tex] f(x)=8(x+0.25)^{2}-0.5 [/tex]------> equation in vertex form
therefore
the answer is
[tex] f(x)=8(x+0.25)^{2}-0.5 [/tex]