BTGModeratorVI wrote: ↑Mon Dec 28, 2020 8:29 am
If y = x^2 - 6x + 9, what is the value of x?
(1) y = 0
(2) x + y = 3
Answer:
A
Source: official guide
Target question: What is the value of x?
Given: y = x² - 6x + 9
Statement 1: y = 0
This tells us that
0 = x² - 6x + 9
Factor the right side to get: 0 = (x - 3)(x - 3)
So, it MUST be the case that
x = 3
Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: x + y = 3
Rearrange this equation to get: y = 3 - x
We're also told that
y = x² - 6x + 9
So, it must be true that x² - 6x + 9 = 3 - x
Rearrange to get: x² - 5x + 6 = 0
Factor: (x - 2)(x - 3) = 0
So,
EITHER x = 2 OR x = 3
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
