If a + b + c = 10 and ab+ bc+ ca = 30, then the value of $a^2 + b^2 + c^2 $ is :
Answer & explanation
Correct answer: option 1
If a + b + c = 10
ab+ bc+ ca = 30,
then the value of $a^2 + b^2 + c^2 $ = ?
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 a + b = 10
ab = 30,
then the value of $a^2 + b^2$ = ?
( a + b )2 = a2 + b2 + 2ab
( 10 )2 = a2 + b2 + 2(30)
100 = a2 + b2 + 60
a2 + b2 = 100 - 60 = 40