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To solve by completing the square you first divide through by 3, then write the result as . Find .

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

Step-by-Step Solution

Dividing by 3 gives . Now halve the coefficient of , so (roots 2 and ; check : 12 − 20 + 8 = 0). Answer forgets the halving step; uses the constant term instead of the -coefficient; is q, the number on the RIGHT of the equation, not .
Answer: D)

Key idea: Method 2: Completing the square

Rewrite into the form .

**Steps for **:
1. Take half the coefficient of .
2. Square it: .
3. Add and subtract this value to complete the perfect square.

Example: .
→
→
→ ±2 → or −5.

Completing the square is how the quadratic formula is DERIVED. It's slower than factorisation but works ALWAYS (no clever guessing required).

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