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When Factorising Fails
When Factorising Fails
Not every quadratic can be factorised nicely. Try factorising x² + 3x - 7 = 0... you can't! The solutions aren't nice whole numbers. That's when the quadratic formula saves the day - it works for EVERY quadratic equation, giving you exact answers (often involving surds).
Visual: The Discriminant and Number of Solutions
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Common Mistakes to Avoid
- WRONG: Forgetting the negative in front of b → writing b instead of -b
- WRONG: Writing -b² instead of (-b)² when b is negative (Use brackets!)
- WRONG: Forgetting to divide the WHOLE top by 2a
- RIGHT: Calculate b² - 4ac separately first, then substitute
Now try it yourself
Quiz · Question 1 of 11
For the equation 3x² − 5x + 2 = 0, what are the values of a, b, and c in the quadratic formula?
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This topic in real past papers
Every real exam question we've found on quadratic formula, with a full worked answer.