Answer:
D) the spring has a length of 1 inch when no force is applied
We have been given an equation of hyperbola
. We are asked to find the center of hyperbola.
We know that standard equation of a vertical hyperbola is in form
, where point (h,k) represents center of hyperbola.
Upon comparing our given equation with standard vertical hyperbola, we can see that the value of h is 6.
To find the value of k, we need to rewrite our equation as:

Now we can see that value of k is
. Therefore, the vertex of given hyperbola will be at point
and option D is the correct choice.
1) $600 deposited at 4% simple interest for one year generates:
$600 * 4% = $600 * 0040 = $24
2) If he wants to earn $132 in interest for the year, he yet needs to generate $132 - $24 = $108 (additional)
3) The interest rate to generate $108 on a deposit of $1200 in a year, at simple interest is:
$1200 * (r) = $108 => r = 108 / 1200 = 0.09 = 9/100 = 9%
Answer: 9%