Quadratic formula
The quadratic formula gives the roots of any quadratic equation ax^2 + bx + c = 0 as x = (-b ± √(b² - 4ac)) / 2a.
Practice This ConceptMain explanation
Teacher explanation
This formula is useful when factorisation is difficult or not obvious. Here a, b, and c are the coefficients from standard form, the expression under the square root is the discriminant, and the ± sign gives two possible roots.
Example
For 2x^2 - 3x - 2 = 0, the formula gives x = 2 or x = -1/2.
Simple analogy
Minus b, plus-minus D, over 2a.
Common confusion
Students often write b with the wrong sign or forget that the denominator is 2a, not just 2.
Exam tip
First write the equation in standard form, then copy a, b, c carefully before substituting into the formula.
Answer writing and exam use
1-mark use
Write the exact meaning of quadratic formula in one clean line.
2-mark use
Define quadratic formula and add one example or condition.
3-mark use
Explain quadratic formula, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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