Question

if a + b + c is equals to 15 and a b + BC + CA is equal to 71 then find the value of a^2+b^2+c^2​

Answer 1

Answer:

according to question

a+b+c =15

ab+bc+ca =71

now we apply (a+b+c)^

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

225 = a^+b^+c^ +2(71)

225- 142 = a^ + b^ +c^

a^+b^+c^ = 83

Answer 2

Hey there,

As, a + b + c = 15 ....... 1.

And ab + bc + ca = 71 ...... 2.

Multiple 2. by 2

Then, 2(ab + bc + ca) = 142

Now by using identity,

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

(15)² = a² + b² + c² + 142

225 - 142 = a² + b² + c²

83 = a² + b² + c²

Hope it help