If p + q = 7 and pq= 5, then the value of p3 + q3 is :
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Correct answer: D
Explanation
The correct answer is Option 4 i.e 238
We know that,
(a + b)3 = a3 + b3 + 3ab(a + b)
Given,
p + q = 7, pq = 5
⇒ (p + q)3 = p3 + q3 + 3pq(p + q)
⇒ p3 + q3 = (p + q)3 + 3pq(p + q)
⇒ p3 + q3 = 73 + 3 × 5 × 7
⇒ p3 + q3 = 343 - 105
⇒ p3 + q3 = 238