Question Number 138123 by Caroline last updated on 10/Apr/21
Answered by Dwaipayan Shikari last updated on 10/Apr/21
$${Det}\left({M}\right)=\mathrm{0} \\ $$$$\Rightarrow−\mathrm{1}\left(\mathrm{8}−\mathrm{20}\right)−\mathrm{4}\left(\mathrm{8}+\mathrm{60}+\mathrm{4}{k}\right)−\mathrm{4}\left(−\mathrm{4}−\mathrm{75}−\mathrm{5}{k}\right)=\mathrm{0} \\ $$$$\Rightarrow\mathrm{12}−\mathrm{272}−\mathrm{16}{k}+\mathrm{316}+\mathrm{20}{k}=\mathrm{0}\Rightarrow\mathrm{4}{k}=−\mathrm{56}\Rightarrow{k}=−\mathrm{14} \\ $$
Commented by mr W last updated on 10/Apr/21
$${k}=−\mathrm{14} \\ $$
Commented by Dwaipayan Shikari last updated on 10/Apr/21
$${Oops}\:!\:{thanks}\:{sir} \\ $$
Commented by Caroline last updated on 11/Apr/21
$${thank}\:{you} \\ $$