Question

If a = 1, b = -2 and c = 3 then find the value of a${}^2$+b${}^2$+c${}^2$+ab+bc+ca.

• A. 9
• B. 3
• C. 1
• D. 6

Answer 1

The correct option is A

9

The given expression is, a${}^2$+b${}^2$+c${}^2$+ab+bc+ca

$\Rightarrow$ (1)${}^2$+(-2)${}^2$+(3)${}^2$+1$\times$ (-2)+(-2) $\times$3+3$\times$1

$\Rightarrow$ 1+4+9-2-6+3 = 9