If x2 + ax + b is a perfect square, then which one of the

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If x² + ax + b is a perfect square, then which one of the following relations between a and b is
true ?

1. a² = b
2. a² = 4b
3. b² = 4a
4. b² = a

Correct Option: B

ax² + bx + c will be a perfect square, if b² = 4ac
∴ x² + ax + b will be a perfect square if a² = 4b
Look : x² + 2√b x + b
= x² + 2.x.√b + (√b)²
= (x + √b)²