Exercise 6 Page 221

The formula for the x -coordinate of the vertex of a parabola is - b2 a, so our first goal will be to find the values of a and b in our function. Since it is already in standard form, we can do that immediately. ax^2+ bx+c ⇔ 1x^2+ 5x+6 We can see that a = 1 and b = 5.

Maximum or minimum value

Before we find the x -coordinate of a vertex, we should make sure that the minimum value of our quadratic function is reached at the vertex. Recall that, if a>0, the parabola opens upwards. Conversely, if a<0, the parabola opens downwards.

In the given function, we have a= 1, which is greater than 0. Thus, the parabola opens upwards and we will have a minimum value at the vertex.

Finding x -coordinate of the vertex

Minimum value of given quadratic function is reached at the vertex. Let's calculate its x -coordinate.

We conclude that the given function reaches its minimum value for x = - 52, which corresponds to option H.