If a3 + b3 +c3-3abc = 250 and a + b + c=10, then what will be the value of (1/5)(ab + bc + ca)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 5
Given that
If a3 + b3 +c3- 3abc = 250 and a + b + c = 10
As we know the formula
a3 + b3 +c3- 3abc = (a + b + c) {(a + b + c)2 - 3 * (ab + bc + ca)}
250 = 10 * { 102 - 3 * (ab + bc + ca)}
3 * (ab + bc + ca) = 100 - 25 = 75
ab + bc + ca = 25
(1/5)(ab + bc + ca) =25/5 = 5