Triangle inequality is correct. The reason why is in post #2 by @anuttarasammyak .Leo Liu said:
An inequality is a mathematical statement that compares two quantities or expressions using symbols such as <, >, ≤, or ≥. It indicates that one quantity is larger or smaller than the other.
An inequality uses symbols to show a relationship between two quantities, while an equation uses an equal sign to show that two expressions are equal. Inequalities also have a range of possible solutions, while equations have only one solution.
The three main types of inequalities are linear, quadratic, and exponential. Linear inequalities involve linear expressions, quadratic inequalities involve quadratic expressions, and exponential inequalities involve exponential expressions.
To solve an inequality, you need to isolate the variable on one side of the inequality symbol and simplify the other side. The solution is the range of values that make the inequality true. However, if you multiply or divide both sides by a negative number, you need to flip the inequality symbol.
Inequalities are important in science because they allow us to represent real-world situations where there is a range of possible solutions. They are used to model relationships between variables in various scientific fields, such as physics, chemistry, and biology.