If a2 + b2 + c2 = 300 and ab + bc + ca = 50, then what is the value of a + b + c ? (Given that a, b and c are all positive.)
Answer & explanation
Correct answer: option 2
If a2 + b2 + c2 = 300
ab + bc + ca = 50
Then what is the value of a + b + c = ?
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
If a2 + b2 = 300
ab = 50
Then what is the value of a + b = ?
( a + b )2 = a2 + b2 + 2ab
( a + b )2 = 300 + 2(50)
( a + b )2 = 400
a + b = \(\sqrt {400}\) = 20