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\(\mathrm{g(x) = (x - 2)(x + 1)(x - 5)}\)The function g is given. Which table of values represents \(\mathrm{y =...

GMAT Advanced Math : (Adv_Math) Questions

Source: Prism
Advanced Math
Nonlinear functions
MEDIUM
...
...
Notes
Post a Query
\(\mathrm{g(x) = (x - 2)(x + 1)(x - 5)}\)

The function g is given. Which table of values represents \(\mathrm{y = g(x) + 4}\)?

A
xy
24
014
-14
B
xy
20
010
-10
C
xy
2-4
06
-1-4
D
xy
28
020
-18
Solution

1. INFER the key insight about polynomial roots

  • Given: \(\mathrm{g(x) = (x - 2)(x + 1)(x - 5)}\) in factored form
  • Key insight: When a polynomial is factored, the roots (where \(\mathrm{g(x) = 0}\)) occur when each factor equals zero:
    • \(\mathrm{x - 2 = 0}\)\(\mathrm{x = 2}\), so \(\mathrm{g(2) = 0}\)
    • \(\mathrm{x + 1 = 0}\)\(\mathrm{x = -1}\), so \(\mathrm{g(-1) = 0}\)
    • \(\mathrm{x - 5 = 0}\)\(\mathrm{x = 5}\), so \(\mathrm{g(5) = 0}\)

2. TRANSLATE the transformation requirement

  • We need \(\mathrm{y = g(x) + 4}\), not just \(\mathrm{g(x)}\)
  • This means: take each \(\mathrm{g(x)}\) value and add 4 to get the corresponding y-value

3. SIMPLIFY the evaluation at each x-value

  • At \(\mathrm{x = 2}\): \(\mathrm{g(2) = 0}\), so \(\mathrm{y = 0 + 4 = 4}\)
  • At \(\mathrm{x = -1}\): \(\mathrm{g(-1) = 0}\), so \(\mathrm{y = 0 + 4 = 4}\)
  • At \(\mathrm{x = 0}\):
    \(\mathrm{g(0) = (0-2)(0+1)(0-5)}\)
    \(\mathrm{= (-2)(1)(-5)}\)
    \(\mathrm{= 10}\)
    so \(\mathrm{y = 10 + 4 = 14}\)

4. INFER which table matches our calculated values

  • We need the table showing: \(\mathrm{(2,4), (0,14), (-1,4)}\)
  • This matches Choice A exactly

Answer: A


Why Students Usually Falter on This Problem

Most Common Error Path:

Weak TRANSLATE skill: Students misread or misunderstand what \(\mathrm{y = g(x) + 4}\) means and think they need to find values for \(\mathrm{g(x)}\) instead of \(\mathrm{g(x) + 4}\).

They correctly identify that \(\mathrm{g(2) = 0}\), \(\mathrm{g(-1) = 0}\), and \(\mathrm{g(0) = 10}\), but forget to add 4 to each value. This leads them to look for a table with values \(\mathrm{(2,0), (0,10), (-1,0)}\).

This may lead them to select Choice B.

Second Most Common Error:

Poor SIMPLIFY execution: Students make arithmetic errors when calculating \(\mathrm{g(0) = (0-2)(0+1)(0-5)}\), possibly getting the wrong sign or missing a step in the multiplication.

If they calculate \(\mathrm{g(0)}\) incorrectly as -10 instead of 10, then \(\mathrm{y = -10 + 4 = -6}\), leading them toward an incorrect table choice. This causes confusion and potentially random guessing among the remaining choices.

The Bottom Line:

This problem tests whether students can correctly apply function transformations while managing the details of polynomial evaluation. Success requires both understanding what the transformation means AND executing the arithmetic correctly.

Answer Choices Explained
A
xy
24
014
-14
B
xy
20
010
-10
C
xy
2-4
06
-1-4
D
xy
28
020
-18
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