Question

if a + b + c is equals to seven and a b + BC + CA is equal to 21 and find the value of a square + b square + c square​

Answer 1

Step-by-step explanation:

Given

a+b+c = 7

ab + bc + ca = 21

a²+b²+c² =?

(a+b+c)² = a²+b²+c² + 2(ab + bc + ca)

(7)² = a²+b²+c² + 2(21)

49 = a²+b²+c² + 42

a²+b²+c² = 49 - 42

a²+b²+c² = 7

Answer 2

Step-by-step explanation:

(a+b+c)

${(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2ab + 2bc + 2ca$

By using this we get

a square + b square +c square =7