Question-138123

Question Number 138123 by Caroline last updated on 10/Apr/21

Answered by Dwaipayan Shikari last updated on 10/Apr/21

Det(M)=0 ⇒−1(8−20)−4(8+60+4k)−4(−4−75−5k)=0 ⇒12−272−16k+316+20k=0⇒4k=−56⇒k=−14

$${Det}\left({M}\right)=\mathrm{0} \\ $$$$\Rightarrow−\mathrm{1}\left(\mathrm{8}−\mathrm{20}\right)−\mathrm{4}\left(\mathrm{8}+\mathrm{60}+\mathrm{4}{k}\right)−\mathrm{4}\left(−\mathrm{4}−\mathrm{75}−\mathrm{5}{k}\right)=\mathrm{0} \\ $$$$\Rightarrow\mathrm{12}−\mathrm{272}−\mathrm{16}{k}+\mathrm{316}+\mathrm{20}{k}=\mathrm{0}\Rightarrow\mathrm{4}{k}=−\mathrm{56}\Rightarrow{k}=−\mathrm{14} \\ $$

Commented by mr W last updated on 10/Apr/21