If p3 + 3p2 + 3p = 7, then the value of p2 + 2p is

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Using Rule 8,
p³ + 3p² + 3p = 7
⇒ p³ + 3p² + 3p + 1 = 7 + 1 = 8
⇒ ( p + 1 )³ = (2)³
⇒ p + 1 = 2 ⇒ p = 2 – 1 = 1
∴ p² + 2p = 1 + 2 × 1 = 3