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StraferKev
Registered User Posts: **260** Junior Member

These are some questions I didn't understand from my practice test. I know it is a lot but I was hoping some could help me explain some of them to me. I think this is also good practice for anyone else who might be taking the Math II subject test soon.

12. The set of points (x,y,z) such that x² + y² + z² = 1 is

A) empty

B) a point

C) a sphere

D) a circle

E) a plane

18. What is the sum of the infinite geometric series

(1/4 + 1/8 + 1/16 + 1/32 + ...)?

A) 1/2

B) 1

C) 3/2

D) 2

E) 5/2

36. The only prime factors of a number n are 2,5,7, and 17. Which of the following could NOT be a factor of n?

A) 10

B) 20

C) 25

D) 30

E) 34

38) If f(x) = 5√(2x), what is the value of f-1 (10)? (the -1 is above the f)

A) 0.04

B) 0.89

C) 2

D) 2.23

E) 22.36

39) The Fibonacci sequence can be defined recursively as

a1 = 1

a2 = 1

an = an-1 + an-2 for n>3.

What is the 10th term of this sequence?

A) 21

B) 34

C) 55

D) 89

E) 144

42) The set of all real numbers x such that √(x²) = -x consists of

A) zero only

B) nonpositive real numbers only

C) positive real numbers only

D) all real numbers

E) no real numbers

45) If log a 3 = x and log a 5 = y, then log a 45 =

A) 2x+y

B) x² + y

C) x²y

D) x + y

E) 9x + y

12. The set of points (x,y,z) such that x² + y² + z² = 1 is

A) empty

B) a point

C) a sphere

D) a circle

E) a plane

18. What is the sum of the infinite geometric series

(1/4 + 1/8 + 1/16 + 1/32 + ...)?

A) 1/2

B) 1

C) 3/2

D) 2

E) 5/2

36. The only prime factors of a number n are 2,5,7, and 17. Which of the following could NOT be a factor of n?

A) 10

B) 20

C) 25

D) 30

E) 34

38) If f(x) = 5√(2x), what is the value of f-1 (10)? (the -1 is above the f)

A) 0.04

B) 0.89

C) 2

D) 2.23

E) 22.36

39) The Fibonacci sequence can be defined recursively as

a1 = 1

a2 = 1

an = an-1 + an-2 for n>3.

What is the 10th term of this sequence?

A) 21

B) 34

C) 55

D) 89

E) 144

42) The set of all real numbers x such that √(x²) = -x consists of

A) zero only

B) nonpositive real numbers only

C) positive real numbers only

D) all real numbers

E) no real numbers

45) If log a 3 = x and log a 5 = y, then log a 45 =

A) 2x+y

B) x² + y

C) x²y

D) x + y

E) 9x + y

Post edited by StraferKev on

This discussion has been closed.

## Replies to: Help: Some Really Hard Questions for the SAT Math II!

2,118Senior Member18. This is equal to (1/2)(1/2 + 1/4 + 1/8 + ...). The sum 1/2 + 1/4 + 1/8 + ... is equal to 1, so the answer is A) 1/2.

36. If 30 is a factor of n, then 3 is a factor of n. This cannot be true, D).

38. Solve f(k) = 10:

5sqrt(2x) = 10 --> x = 2, C).

39. Might help to write the terms out (if you haven't memorized the sequence):

1,1,2,3,5,8,13,21,34,55

The tenth term is 55, C).

42. It helps to know that the absolute value of x is sometimes defined as

|x| = sqrt(x^2).

Here, you're essentially solving |x| = -x, in which the solution is the set of non-positive real numbers, B).

45. Apply logarithm identities:

log 45 = log 9 + log 5

= 2 log 3 + log 5

= 2x + y, A).

260Junior Member2,118Senior Member