Complete the square than convert to vertex form. y=2x^2+8x-9

There are 2 roots so the only way to complete the square is,

Just factor 2 out of 2x^2+8x (just ignore the -9) then find the number that will make the terms be able to complete the square.

then complete the square and multiply 2 inside the brackets.

subtraction as you already get the vertex form and know how to complete the square.

Vertex Form: