If a + b = 7, what is the value of a³ + b³ + 21ab?
Show answer & explanation
Correct answer: D
Explanation
a + b = 7
According to the formula:
a³ + b³ + 3ab(a + b) = (a + b)³
a³ + b³ + 21ab = a³ + b³ + 3ab(a + b)
⇒ = (a + b)³
= 7³
= 343
SSC CPO 2025 PYQ — Question 143
SSC CPO - 10 Dec 2025 - Shift 2 • Quantitative Aptitude • Q143