If a + b = 8 and ab = 12, then the value of a3 + b3 is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 224
|
Understanding Tricks |
|
Application a + b = 8 (a + b2) = 82 a2 + b2 + 2ab = 64 a2 + b2 = 64 - 2ab a2 + b2 = 64 - 24 a2 + b2 = 40 |
|
Now a3 + b3 = (a + b) (a2 + b2 - ab) = 8(40 - 12) = 8 × 28 = 224 |