Question

a+b+c =0 then a^2+b^2+c^2÷c^2-ab

Answer 1

$a + b + c = 0 \\ a + b = - c \\ (a + b) { }^{2} = ( - c) {}^{2} \\c {}^{2} = a {}^{2} + b {}^{2} + 2ab \\ \\ a {}^{2} + b {}^{2} + c {}^{2} \div c {}^{2} - ab \\ a {}^{2} + b { }^{2} + a {}^{2} + b {}^{2} + 2ab \div a {}^{2} + b {}^{2} + 2ab - ab \\ 2a {}^{2} + 2b {}^{2} + 2ab \div a {}^{2} + b {}^{2} + ab \\ 2(a {}^{2} + b {}^{2} + ab) \div a {}^{2} + b {}^{2} + ab \\ 2 \: \: \: (ans)$