Bunuel
If (x^2 + 2x - 9)/3 ≤ x + 1, then x could be represented by which of the following?
A. − 4 ≤ x ≤ − 3
B. − 4 ≤ x ≤ 3
C. − 3 ≤ x ≤ 3
D. − 3 ≤ x ≤ 4
E. 3 ≤ x ≤ 4
Start by getting rid of the fraction by multiplying by 3
\(x^2+2x-9 \leq 3x+3\)
Gather all terms on the left hand side and factor it
\(x^2-x-12 = (x-4)(x+3) \leq 0\)
From here we need to decide what to do with the inequality. If it was an equation, then we would know that \(x=4\) and \(x=-3\). Those points will be limits of the range we want to consider. Right away we can see that the only answer choice with these limits is answer D. It would have been slightly trickier if some answer choices looked like \(x\leq-3\) and \(x\geq4\). That way we would have to worry about the direction of the inequality and @TeamGMATIFY's hint becomes super helpful.
If you like geometry and conic sections, you will recognize that \(f(x)=x^2-x-12\) is a parabola opening upward. The question asking for what values of x is the parabola \(\leq0\). Because the parabola is opening upwards, we know that the parabola \(f(x)\) will be negative in between the points where it crosses the x-axis. Those are the points we found by solving \(x^-x-12=0\). If you plotted it it would looks like this:

We can see that it crosses the x-axis at x=-3 and x=4, and is negative everywhere in between.