SAT math help?

Test Preparation SAT Preparation
1

<p>An explanation of these would be wonderful!</p>

<p>For all x, let the function f be defined by f(x) = a(x-h)^2+k, where a, h, and k are constants. If a and k are positive, which of the following CANNOT be true?
(for this one instead of plugging numbers in is there a way to do it?)
a. f(10)=1
b. f(0)=-5 ANSWER
c. f(0)=5
d. f(1)=-h
e. f(-1)=h</p>

<p>~</p>

<p>For any cube, the volume is V and the surface area is A. V is directly proportional to which of the following?</p>

<p>a. A
b. A^2
c. A^3
d. A^(2/3)
e. A^(3/2) ANSWER</p>

2

<p>Plug 4 for a surface and see what answer matches 8 as a volume. This is obviously a 2-2-2 cube.</p>

<p>Start with bottom since the first three suggestions are easy to reject.</p>

3

<p>1) (x-h)^2 is non-negative and a is positive so a(x-h)^2 is non-negative. Also, it is given that k is positive so (x-h)^2+k is positive. -5 is negative so it can’t be the answer.</p>

<p>2) A is proportional to s^2 and V is proportional ( actually equal to) s^3. Note that A^(3/2) is proportional to s^3, which is V.</p>

4

<p>for the first question u have that a is +ve which means that the parabola is looking up and k is also +ve so f(x) or y can never be a -ve number </p>

<p>2) if u have for example
v^3 and A^2 ( as in this quest.)
u want volume in terms of area , u want A^2 to be A^3
so u will put needed over original
a^3/2</p>

5

<p>Hey guys, thanks for your answers but I’m confused about the second one
Isn’t the surface area for a cube 6a^2? isn’t a^2 just the area?</p>

6

<p>You are correct that the surface area for a cube is A=6s^2. But the 6 is irrelevant in this problem because they only want to know what V is DIRECTLY PROPORTIONAL to, not what it is EQUAL to.</p>

<p>Also, A=s^2 is the area of a square (not relevant to this problem).</p>