The vertex of this parabola is at (2,-1). when the y-value is 0, the x-value is 5. what is the coefficient of the squared term in the parabolas equation

We know that

case a)
the equation of the vertical parabola write in vertex form is
y=a(x-h)²+k,
where (h, k) is the vertex.

Using our vertex, we have:
y=a(x-2)²-1
We know that the parabola goes through (5, 0),

so
we can use these coordinates to find the value of a:
0=a(5-2)²-1
0=a(3)²-1
0=9a-1

Add 1 to both sides:
0+1=9a-1+1
1=9a
Divide both sides by 9:
1/9 = 9a/9
1/9 = a
y=(1/9)(x-2)²-1

the answer is
a=1/9

case b)
the equation of the horizontal parabola write in vertex form is
x=a(y-k)²+h, 
where (h, k) is the vertex.

Using our vertex, we have:
x=a(y+1)²+2, 
We know that the parabola goes through (5, 0),

so
we can use these coordinates to find the value of a:
5=a(0+1)²+2
5=a+2
a=5-2
a=3
x=3(y+1)²+2

the answer is
a=3

see the attached figure