Please submit your concern

Question:

If a³ - b³ = 2349 and (a - b) = 9, then (a + b)² - ab is equal to:

Explanation:

(a - b) = 9               ...(1)

(a - b)³ = 729

a³ - b³ - 3ab(a - b) = 729

2349 - 3ab(9) = 729

27ab = 1620

ab = 60                ...(2)

(a - b) = 9

(a - b)² = 81

a² + b² - 2ab = 81

a² + b² - 2(60) = 81

a² + b² - 120 = 81

a² + b² = 201        ...(3)

(a + b)² - ab = a² + b² + 2ab - ab

= a² + b² + ab

= 201 + 60

= 261

Hence, the correct answer is Option C