GMAT Quant Chapter 19: Functions and Sequences

Question 1

What must we always remember when dealing with the domains of functions on the GMAT?

Answer 1

We can’t take the square root of a negative number
We aren’t allowed to divide by 0

Question 2

How should we approach compound functions (when one function is nested inside another function)?

Answer 2

the output of the first function becomes the input of the second function

Question 3

What line test can we use to test whether a graph (line) is a function?

Answer 3

The vertical line test.

Draw a straight line. If the graph of the line intersects the straight line more than once then it cannot be a function because one input for a function results in one output.

Question 4

What is the difference between an explicit sequence and a recursive sequence?

Answer 4

An explicit sequence defines the sequence in terms of a defined relationship whereas a recursive sequence defines the sequence by using preceding terms.

Question 5

What is the formula for an arithmetic sequence that can only be used for arithmetic sequences?

What formula can we use to sum the first n terms of an arithmetic (NOT RECURSIVE) sequence?

Answer 5

An = A1 + (n-1)d

Sn = n/2 (a1 + an)

Question 6

What is a geometric sequence?

What is the formula for a geometric sequence?

Answer 6

When the ratio between every pair of two terms is always the same.

An = A1 + R ^n-1