Question

please help :(

Use the function y=-2(x+2)(2x+8). What are the x- intercepts of the functions graph. What are the coordinates of the graphs vertex

Answer 1

we want to get this into vertex form first.
vertext form looks like:
y = a(x-h)^2 + k


so, we FOIL to get rid of the ( ) ( )
y=-2(x+2)(2x+8).
y=-2(2x^2+8x+4x+16)
y=-2(2x^2+12x+16)

now we pull out the constant of 16 from the ( )
y=-2(2x^2+12x) +16(-2)
y=-2(2x^2+12x) +(-32)

now we complete the square for the (2x^2 + 12x) portion of the equation, can you do this for me?