If a + b + c = 10 and $a^2 + b^2 + c^2 = 48$,then the value of ab + bc + ca is _______.
Answer & explanation
Correct answer: option 2
If a + b + c = 10 and $a^2 + b^2 + c^2 = 48$
then the value of ab + bc + ca = ?
If the number of equations are less than the number of variables then we can put the extra variables according to our choice =
So here two equations given and three variables are present so put c = 0
a + b = 10
$a^2 + b^2 = 48$
then the value of ab =
( a + b )2 = a2 + b2 + 2ab
(10)2 = 48 + 2ab
100 - 48 = 2ab
2ab = 52
ab = 26