In order to write this quadratic equation in standard form, first note that standard form is ax^2+bx+c for quadratics, where c is the numerical value (constant), B is the coefficient of x, and a is the coefficient of x^2 and is the leading coefficient. Next, multiply the binomials of (x-7) and (x-1). You can do this by using FOIL, or by distributing each of the terms in a binomial to each of the other terms in the other binomial. (Please let me know if you need a walk through in this step in particular). Furthermore, you should then write y= (the simplified trinomial). Now, the quadratic is in standard form. To reiterate, just simplify the two binomials by multiplying them together and writing that they're equal to y.
Complete the square:
F(x) = -3x² - 6x - 5
F(x) = -3 (x² + 2x) - 5
F(x) = -3 (x² + 2x + 1 - 1) - 5
F(x) = -3 ((x + 1)² - 1) - 5
F(x) = -3 (x + 1)² + 3 - 5
F(x) = -3 (x + 1)² - 2
The y-intercept has x-coordinate equal to 0, so it corresponds to the value of F(0) :
F(0) = -3 (0 + 1)² - 2 = -3 - 2 = -5
The axis of symmetry is the vertical line running through the vertex of this parabola, so we'll come back to this.
The vertex of the parabola is (-1, -2). This represents the maximum value of F(x), which follows from
(x + 1)² ≥ 0 ⇒ -3 (x + 1)² ≤ 0 ⇒ -3 (x + 1)² - 2 ≤ -2
This is to say, every point on the parabola has a y-coordinate no greater than -2.
As mentioned earlier, the axis of symmetry is the vertical line through the vertex, and its equation is determined by the x-coordinate of the vertex. Hence the AoS is the line x = -1.
