Complete the square to re-write the quadratic function in vertex form:
y = x2 + 4x – 9

− 2 ± √ 13

Step-by-step explanation:

(-b±√(b²-4ac))/(2a)

Plug in and solve.

y = (x + 2)² - 13

Step-by-step explanation:

y = x² + 4x - 9

To complete the square

add/ subtract ( half the coefficient of the x- term)² to x² + 4x

y = x² + 2(2)x + 4 - 4 - 9

  = (x + 2)² - 13 ← in vertex form

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this

answer: f true

step-by-step explanation: