Question

If a + b + c = 7 and ab + bc + ca = 20, find the value of a^2 +
b² + c²​

Answer 1

Answer:

9

Step-by-step explanation:

Given:

a + b + c = 7

ab + bc + ca = 20

from the formula of (a +b +c)²= a²+b²+c²+2 (ab + bc + ca),

(7)² = a²+b²+c²+2 (20)

49 = a²+b²+c²+ 40

a²+b²+c² = 49-40 = 9

Note: if we don't know (a +b +c)², multiply (a +b +c) X (a +b +c) manually.