Hi. Were you expecting some value of y to be given? Symbol y never appears in the

equation for a vertical line because its value can be any

Real number.

Was all of this wording given to you?

If so, it seems like they want you to first find values for A and B. There is a much simpler approach (my opinion) for finding the value of x that leads to the shortest vertical distance between the parabolas.

I solved it by using the given quadratic functions to express the distance AB in terms of x (not in terms of A and B, which I ignored).

The expression for the distance AB (in terms of x) is a differentiable

function. We can use its first derivative, to find its minimum value.

Does the given diagram look anything like this? (Vertical line omitted, for now).

The top blue line is y = A.

The bottom blue line is y = B.

The top green line is y = 7.

The bottom green line is y = 4.

jeane9.jpg
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