The Answer is b. Hope that helps
-2 is the answer when i figured out the problem
<span>We let x be the length and y be the width of the rectangle. Then,
Perimeter = 2x + 2y
100 = 2x + 2y
50 = x + y
y = 50 - x
Area = xy
A = x(50 - x)
A = 50x - x^2
We then take the derivative; set it equal to zero:
A ' = 50 - 2x
0 = 50 - 2x
2x = 50
x = 25
y = 50 - x
y = 50 - 25
y = 25
Therefore, the dimensions are 25 and 25.</span>
the correct answer should be (b) 6 is extraneous.
If you look at the second row of the solution you see (x-6) as a factor in one of the denominators. That's a problem: if 6 were a solution this denominator would become 0. But denominators being 0 is bad (undefined), so while 6 comes out of the algebraic manipulation as a solution, it is invalid, or extraneous.
-3 is a fine solution.