Question

ifa+b-c=9 and ab+bc+ca =26,find
a^2+b^2+c^2.

Answer 1

${(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2(ab + bc + ca) \\ {9}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2 \times 26 \\ {a}^{2} + {b}^{2} + {c}^{2} = 81 - 52 = 29$