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Solve using the quadratic formula.

Class 10Quadratic EquationsAlgebra — Quadratics
  • A
  • B
  • C
  • D

Step-by-Step Solution

, so . The first option flips the sign of −b. The third option is correct before simplifying but was then "simplified" by halving only the 6 and the 10 while leaving untouched. The last option halves the numerator and denominator without taking the factor 2 out of first.
Answer: B)

Key idea: Method 3: The quadratic formula

The general solution to (any quadratic):

** = [− ± √] /

Derivation: complete the square on in full generality.

**Always works** when ≥ 0. When , no real roots exist (complex roots only — Class 11 territory).

**Example**: = (5 ± 1) / 6 → or 2/3.

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