If a + b + c = 7 and ab + bc + ca = 1, then a3+ b3 + c3 – 3abc is equal to:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 322.
⇒ a3 + b3 + c3 – 3abc = (a + b + c)[(a + b + c)2 – 3(ab + bc + ca)]
Given,
⇒ (a + b + c) = 7 and,
⇒ (ab + bc + ca) = 1
Applying the formula:
⇒ a3 + b3 + c3 – 3abc = 7 × (49 – 3 × 1)
⇒ (7 × 46) = 322