Mathematics for IGCSE & O level - Algebraic Manipulation (Section 4 - No. 33)
When factoring a quadratic expression, how do you confirm your factored form is correct?
Multiply the factors to see if you get the original expression.
Divide the original expression by one of the factors
The factored form is always correct.
Compare the factored form with a standard form table.
Explication
Multiplying the factored form back out should result in the original expression.