Joe S. answered 05/01/20
Former teacher with perfect score on Math GRE
This question is asking you to find the vertex of the parabola since it will be the highest or lowest point of the quadratic equation. First, we will calculate the x-value at the vertex using a formula, then we will plug the x-value into the quadratic equation to find the y-value of the vertex.
To find the x-value of the vertex of a quadratic function, use the formula:
-b / 2a
where b is the constant by x, and a is the constant by x2 . This is a standard formula. In this case:
a = 3
b = -30 (don't forget the negative sign!)
Now we can plug these into the formula to find the x-value of the vertex:
x-value = -b / 2a
x-value = -(-30) / (2 x 3)
x-value = 30 / 6 = 5
The x-value at the vertex is 5. To find the y-value at the vertex, plug the x-value we just found into the quadratic function:
f(x) = 3x2 - 30x + 73
f(5) = 3(5)2 - 30(5) + 73 = -2
The y-value at the vertex is -2, so our vertex is at (5,-2). Since the y-value at the vertex will always be the minimum or maximum value of a quadratic equation, -2 is the minimum or maximum value.
Please message me if you would like more explanation or have another question.
Lilly R.
Thank you05/01/20