if a2+ b2= 135 and ab = 7, (a > 0, b > 0) then the value of (a3– b3) ?
Show answer & explanation
Correct answer: B
Explanation
Correct Answer is option 2 i.e.1562
|
Concept |
Understanding |
Application |
Fair calculation |
|
a3– b3 = (a – b) (a2 + b2+ ab) |
Given: a2 + b2 = 135 and ab = 7 (a > 0, b > 0) |
(a – b)2 = a2 + b2 – 2ab (a – b)2 = 135 – 14 = 121 (a – b) = 11 Now, a3 – b3 = (a – b) (a2 + b2 + ab) = 11 × (135+7) = 1562 |
11 × (135 + 7) = 11 × 142 = 1562 |