Question

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

Answer 1

Answer:

(a+b+c)(a+b+c+) =a(a+b+c+)+b(a+b+c+)+c(a+b+c)

$= {a}^{2} + ab + bc + ba + {b}^{2} + bc + ca + cb + {c}^{2}$

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