Question

The vertex of the graph of a quadratic function is (2, –1) and the y-intercept is (0, 7). Which of the following is the equation of the function? A. y = 2x2 – 8x + 7 B. y = 2x2 + 8x + 7 C. y = 2x2 + 8x – 7 D. y = 2x2 – 7x + 8

Answer 1

The asnwer is C, y=2x2+ 8x-7

Explanation:

Answer 2

The correct answer is A) 2x^2 - 8x + 7

Explanation:

To start, we know the constant at the end must be 7, since the intercept is 7. This leaves us with just answers A and B.

Next, we know the x value of the vertex (2), should be equal to -b/2a, in which b is the coefficient of x and a is the coefficient of x^2. So, we input the values from A and B to see which one satisfies that fact.

-b/2a = x value

-(-8)/2(2) = 2

8/4 = 2

2 = 2

Since this is true, we know that A is the correct answer. We can also try it with B just to check, but it does not work.