Discussion
Let \(x\) be a real number such that \(7x + 4 \lt 9x + 8\) . Then the solution set of the inequality is
Answer: C
The solution set is \((-2, \infty)\).
Collect x on one side.
\[ \begin{aligned} 7x + 4 &\lt 9x + 8 \\ -4 &\lt 2x \\ x &\gt -2 \end{aligned} \]
The inequality is strict, so -2 itself is excluded and the bracket at -2 is round, which rules out \([-2, \infty)\). \((-\infty, -2)\) reverses the inequality, a slip that happens when dividing by a negative number that is not actually there.
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