I can't see the photo ....
Let
x-------------> amount added <span>to each side
</span>A-------------> area increased----------> 84 ft²
we know that
A=(10+x)*(5+x)=84-----------> 10*5+10*x+5*x+x²
50+15x+x²=84----------> x²+15x-34=0
<span>solving the second order equation
</span>x1=-17
x2=2
the answer is x=2 ft
<h2>
Explanation:</h2><h2>
</h2>
Here you haven't provided any function, so I'll assume this one:

This is a quadratic function whose graph represents a parabola. Any parabola has its vertex at the point:

Therefore:

Therefore, the vertex is:

Answer:
A.
Step-by-step explanation: