Answer:
No she isn't. The value of [tex]a[/tex] is [tex]a=-\frac{1}{45}[/tex]
Step-by-step explanation:
We know that all quadratic equation can be written in the following way :
[tex]y=ax^{2}+bx+c[/tex] (I)
Where [tex]a,b[/tex] and [tex]c[/tex] are real numbers.
I will attach a drawing with the quadratic graph to understand the situation.
We know by looking at the drawing and analyzing it that the parabola passes through the points : [tex](0,0) ; (60,80)[/tex] and [tex](120,0)[/tex]
[tex](0,0)[/tex] because we put our coordinates origin there.
[tex](120,0)[/tex] because that's where the golf hole is.
And [tex](60,80)[/tex] because we know that its highest point reaches 80 feet up in the air at the middle of the distance between its roots (property of a negative parabola).
Finally, we work with the three points and the equation (I) in order to find the values of [tex]a,b[/tex] and [tex]c[/tex] ⇒
The parabola passes through [tex](0,0)[/tex] ⇒
[tex]y=ax^{2}+bx+c[/tex] ⇒
[tex]0=a(0)^{2}+b(0)+c[/tex] ⇒ [tex]c=0[/tex]
The parabola passes through [tex](60,80)[/tex] ⇒
[tex]80=a(60)^{2}+b(60)[/tex] ⇒
[tex]80=3600a+60b[/tex] (II)
The parabola passes through [tex](120,0)[/tex] ⇒
[tex]0=a(120)^{2}+b(120)[/tex] ⇒
[tex]0=14400a+120b[/tex]
[tex]120b=-14400a[/tex]
[tex]b=-120a[/tex] (III)
Now if we use (III) in (II) ⇒
[tex]80=3600a+60(-120a)[/tex]
[tex]80=3600a-7200a[/tex]
[tex]3600a=-80[/tex]
[tex]a=-\frac{1}{45}[/tex] ⇒ [tex]b=\frac{8}{3}[/tex]
Finally the equation of the parabola is
[tex]y=-\frac{x^{2}}{45}+\frac{8}{3}x[/tex]
Where the value of [tex]a[/tex] is [tex]a=-\frac{1}{45}[/tex]
