Enter an expression in the box to write a quadratic function given the vertex (7,-4) and the point (5, 8).

Step-by-step explanation:

The vertex form of an equation of the parabola:  

                                                       f(x) = a(x - h)² + k

the vertex is (7, -4)  ⇒   h = 7,  k = -4

so:

     f(x) = a(x - 7)² + (-4)

    f(x) = a(x - 7)² - 4

The parabola goes through the point (5, 8) ⇒   x=5,  f(x)=8

8 = a(5 - 7)²  - 4

8 = a(-2)²  - 4

+4           +4

12  = 4a

÷4       ÷4

a = 3

It means the equation of the parabola in vertex form:

                               f(x) = 3(x - 7)² - 4

i get you, what you should do is think of the positive things that would come out of it. it will make yours parents proud and raise your grade. you should always try and if you can't focus tell the teacher.