Question

if a + b + C is equal to 9 and a b + BC + CA equal to 26 find a square + b square + c square

Answer 1

a+b+c=9

(a+b+c)^2=9^2

=a^2+b^2+c^2+2(ab+bc+ca)=81

=a^2+b^2+c^2+52=81

=a^2+b^2+c^2=81-52=29

hope the answer is correct

Answer 2

Identity to be used: (a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca

Given:

a + b + c = 9

ab + bc + ca = 26

To find: a^2 + b^2 + c^2

Answer:

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

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

9^2 = a^2 + b^2 + c^2 + 2*26

81 = a^2 + b^2 + c^2 + 52

a^2 + b^2 + c^2 + 52 = 81

a^2 + b^2 + c^2 = 81 - 52

a^2 + b^2 + c^2 = 29

Hope it helps :)