The first error in Jan'ai's work in determining the considered function is given by: Option D: She incorrectly determined the x-coordinate of the vertex.
<h3>What are the coordinates of vertex for a quadratic function?</h3>
For a quadratic function of the form , its vertex form is obtained as:
For the form , the vertex has coordinates (h, k)
Thus, for the obtained equation , we get the coordinates of vertex as:
,
Thus, the coordinates of vertex of is:
The missing steps of work of Jan'ai are:
- Begin to write a function in factored form.
- Substitute x = 0, y = f(x) = -25 to determine a.
- Simplify and solve to find a.
- Rewrite the function.
- Rewrite in standard form.
- Find the x-coordinate of the vertex.
- Find the y-coordinate of the vertex.
so (-2,35) is the coordinate of the vertex, which denotes the minimum.
So, as we see, in the 5th step, Jan'ai had the quadratic function ,
Comparing this to , we get a = 5, b = -20, c = -25
The vertex's x-coordinate will be on -b/2a = -(-20)/ 2(5) = 20/10 = 2
But Jan'ai didn't putted that negative sign before b. in the 6th step.
Thus, the first error in Jan'ai's work in determining the considered function is given by: Option D: She incorrectly determined the x-coordinate of the vertex.
Learn more about the vertex form of a quadratic equation here:
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