Does The Equation y = (x – p)(x – q) Intercept The x-axis At GMAT Data Sufficiency

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Question: Does the equation y = (x – p)(x – q) intercept the x-axis at the point (2,0)?
(1) pq = -8
(2) -2 – p = q

  1. Statement (1) ALONE is sufficient but statement (2) ALONE is not sufficient.
  2. Statement (2) ALONE is sufficient but statement (1) ALONE is not sufficient.
  3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
  4. EACH statement ALONE is sufficient.
  5. Statements (1) and (2) TOGETHER are not sufficient.

‘Does the equation y = (x – p)(x – q) intercept the x-axis at the point (2,0)?’ - is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book "GMAT Quantitative Review". GMAT Quant section consists of a total of 31 questions. GMAT Data Sufficiency questions consist of a problem statement followed by two factual statements. GMAT data sufficiency comprises 15 questions which are two-fifths of the total 31 GMAT quant questions.

Solution and Explanation

Approach Solution 1:

There is only one approach to this problem.

Given in the question an equation y = (x-p)(x-q)
This is the equation of a line and it is asked whether it intercepts at the x-axis at the point (2,0) or not.
This is a question from coordinate geometry.
The point (2,0) lies on the x axis as the y value is 0.
Therefore we need to find the x-intercept of the given line.
The x-intercept of the given line will be when y = 0
(x - p)(x - q) = 0
There are two values of x for which this equation can be 0
Either x- p = 0
Or x-q = 0
This means either x = p or q
This line has x intercept either (p,0) or (q,0)
We are given two statements and we have to check if these equations are sufficient to get the answer or not.
In statement 1,
Given : pq = -8
This statement is not sufficient to say whether p = 2 or q = 2.
Coming to statement 2,
Given: -2 - p = q
This statement is also not sufficient to say whether p = 2 or q = 2.
Now taking both the statements into consideration we get,
Pq = -8
And -2 -p = q
Putting the value of q in equation 1
p(-2-p) = -8
-2p - \(p^2\)= -8
\(p^2\)+ 2p - 8 = 0
\(p^2\)- 2p + 4p - 8 = 0
p(p-2) + 4(p-2) = 0
(p-2)(p+4) = 0
P = 2 or -4
Putting p = 2 in statement 2 we get
-2-2 = q
Q = - 4
Putting p = -4 in statement 2 we get,
-2 + 4 = q
Q = 2
In either case one of the variables is 2 so y=(x−p)(x−q) intercepts the x-axis at the point (2,0).
Therefore the correct answer is option C
Correct Answer: C

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