Zero product principle
If the product of two expressions is zero, then at least one of the expressions must be zero.
Practice This ConceptMain explanation
Teacher explanation
This principle is the bridge between factorised form and final roots. Once a quadratic equation is written as a product, each factor is set to zero separately.
Example
(x - 4)(x + 2) = 0 gives x = 4 or x = -2.
Simple analogy
Zero product means zero in one bracket at least.
Common confusion
Students sometimes solve by adding the factors instead of setting each factor to zero.
Exam tip
After factorisation, never keep the product equal to zero only; split it into two separate equations.
Answer writing and exam use
1-mark use
Write the exact meaning of zero product principle in one clean line.
2-mark use
Define zero product principle and add one example or condition.
3-mark use
Explain zero product principle, show the method or example, and mention the common mistake.
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