Hello,
Please, see the detailed solution in the attached files.
Thanks.
The mean is 85*0.39 = 33.15, while the standard error is sqrt(0.39*0.61/85) = 0.0529. Using the z-score of 1.96, the confidence interval is:33.15 +/- 1.96*0.0529 = (33.05, 33.25)By dividing by 85, this corresponds to a proportion of:(0.3888, 0.3912)
20 shares at 10 1/2 (or 10.5) = 20 * 10.5 = 210
20 shares at 11 1/4 (or 11.25) = 20 * 11.25 = 225
so the profit made would be : 225 - 210 = $ 15 <==
Your x values are 1.24 and -0.404.
First you need to make the equation equal 0, and you can do this simply by subtracting 5x, so you get
6x² - 3 - 5x = 0
The quadratic formula is (-b +- √b² - 4ac)/2a, where a is the x², b is the x, and c is the value. This means we can just substitute it in.
You find the value of the part inside the square root, which is -5² - 4 × 6 × -3 = 97. Now we can use this to substitute in to (5 +- √97)/12. We can do it with the plus sign, and get 1.24, and then with the subtract sign and get -0.404.
I hope this helps!