Monday, July 19th, 2010
Solution:
First recognize that this is in the form of (x2-a2), which can always be factored as (x+a)(x-a). If you multiply these two terms, you get x2-ax+ax-a2, which is equal to x2-a2.
So in this case, we can see that a=3,
so x2-9
= x2-32
= (x+3)(x-3)
Monday, July 19th, 2010
Solution:
A function is a type of relation, i.e. it relates one set of numbers to another. The function (call it “f”) takes any member of one set (call it “x”) and connects it to a unique member of another set. Symbolically, we write this unique member of the other set as f(x). You can say “f of x” when you see this rotation.
Now, we can write the function as a rule or equation. For example, f(x) = 2x. In this example, each value of x as assigned double its value by the function f.
Monday, July 19th, 2010
Solution:
You can simply 12 – ( x + 3 ) +10 by rearranging the terms:
- 12 –x -3 +10
- 19-x
Saturday, July 17th, 2010
Solution:
1. Let’s call the number of cookies Cara made “x”
2. First she sold three fifths of x(.6x)
3. The remaining amount is two fifths of x(.4x)
4. Then she one fourth of x;two fifths of “x” (.25*.4x = .1x)
5. .6x=.1x+200
6. .5x=200
7. x= 400
Saturday, July 17th, 2010
Here’s how you solve this type of question:
- Start with an equation like 3x + 5y = 15
- Move 3x to the other side, so 5y = 15 – 3x
- Divide both sides by 5, so y = 3 – x
- Another way of writing this is y = -.6x + 3, or y=mx = b, where m=-0.6 and b = 3
- If m = -0.6, that means that the slope =-0.6
Saturday, July 17th, 2010
Solution:
- 2(x – 5) = -11
- 2x – 10 = -11
- 2x = -1
- x = -0.5
Saturday, July 17th, 2010
Solution:
This is a well known “trick question”. It’s simply a series of squares with the digits reversed:
12 = 1 => 1
22 = 4 => 4
32 = 9 => 9
42 = 16 => 61
52 = 25 => 52
62 = 36 => 63
72 = 49 => 94
82 = 64 => 46
92 = 81 => 18
Saturday, July 17th, 2010
Here’s how you solve this type of question:
- The base of the 3D rectangle is in the shape of a 2D rectangle.
- Multiply the length of this 2D rectangle by its width to let the area
Saturday, July 17th, 2010
Solution:
The arithmetic mean is the average.
http://en.wikipedia.org/wiki/Arithmetic_mean