Question

The area of a rectangle is x^2 + 4x - 5. If we factored this out, we would get the lengths and widths of the sides of the rectangle. For what value(s) of x would these side lengths not make any sense? Why?

Answer 1

If X ≤ 1, these side lengths has no sense.

Explanation:

We can factored the expression X² + 4X - 5 in a expression in the form:

(X+a) (X+b)

Where a*b = -5 and a+b = 4

That means a could be 5 and b = -1:

(X+5) (X-1)

The side lenghts of the rectangle will not have any sense if ≤ 0. With the factored expression:

(X+5) ≤ 0 ; If X ≤ -5, these side lengths has no sense.

Also:

(X-1) ≤ 0; If X ≤ 1, these side lengths has no sense.

Both expressions are resumed in:

If X ≤ 1, these side lengths has no sense.