If a + b = 10 and a2 + b2 = 58, find the value of ab.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 21.
Given that
If a + b = 10 and a2 + b2 = 58
Formula used
(a + b)2 = a2 + 2ab + b2
Calculation
⇒ 100 = 58 + 2ab
⇒ 2ab = 100 - 58 = 42
⇒ ab = 21