2x² - 128
2(x² - 64), but (x² - 64) = x² - 8² (difference of 2 squares),[a²-b²=(a-b)(a+b)]
2(x² - 64) = 2(x² - 8²) = 2(x-8)(x+8)
The amount it is increasing by, 3 is added each time.
10 pieces of silverware laid in a row if 3 are identical spoons, 4 are identical forks, and 3 are identical knifes
The arrangement of 'm' objects on which 'n' objects are of same kind is 
Given: 10 pieces of silverware so its 10!
3 are identical spoons so its 3!
4 are identical forks so its 4!
and 3 are identical knifes so its 3!
Arrangements made =
= 4200
To solve for the last side of the triangle, use the Pythagorean Theorem:
(8)^2 + x^2 = (9)^2
x = sqrt of 17
However, this is a NEGATIVE sqrt 17 because the terminal side is in quadrant 4, meaning that this side is under the X-axis and therefore negative.
Now that you know the side opposite of u in the triangle, do opposite/hypotenuse.
sin u = -(sqrt 17)/9