Find the value of a² + b² + c², when a + b + c = 9 and ab + bc + ca = 20?

None of these

Given a + b + c = 9 and ab + bc + ca = 20

We know that (a + b + c)² = a² + b² + c² + 2(ab + bc + ca)

Substituting the given values:

(9)² = a² + b² + c² + 2(20)

81 = a² + b² + c² + 40

Now, find a² + b² + c²:

a² + b² + c² = 81 - 40

= 41