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Category: Matrices and Determinants

Question-205306

Question Number 205306 by peter frank last updated on 15/Mar/24 Answered by A5T last updated on 15/Mar/24 $$\mathrm{2}\left(\mathrm{3}{x}^{\mathrm{2}} +\mathrm{4}{xy}\right)=\mathrm{450}\Rightarrow\mathrm{3}{x}^{\mathrm{2}} +\mathrm{4}{xy}=\mathrm{225} \\ $$$$\Rightarrow{y}=\frac{\mathrm{225}−\mathrm{3}{x}^{\mathrm{2}} }{\mathrm{4}{x}}\Rightarrow{v}=\mathrm{3}{x}^{\mathrm{2}} {y}=\frac{\mathrm{3}{x}\left(\mathrm{225}−\mathrm{3}{x}^{\mathrm{2}} \right)}{\mathrm{4}}…

If-A-M-2-2-det-A-0-A-3-A-2-A-Find-the-values-of-det-2A-I-

Question Number 202371 by mnjuly1970 last updated on 25/Dec/23 $$ \\ $$$$\:\:\:{If}\:\:\:\:{A}\:\in\:{M}_{\mathrm{2}×\mathrm{2}} \:,\:{det}\left({A}\:\right)\neq\:\mathrm{0} \\ $$$$\:\:\:\:,\:\:{A}^{\:\mathrm{3}} \:=\:{A}^{\mathrm{2}} \:+{A}\:\Rightarrow\:{Find}\:{the}\: \\ $$$$\:\:\:\:{values}\:{of}\:\:\:{det}\:\left(\mathrm{2}{A}\:−{I}\:\right) \\ $$$$ \\ $$ Answered by…

Find-all-possible-value-a-a-b-d-b-a-b-c-c-b-c-d-d-a-c-d-when-a-b-c-d-vary-over-positive-reals-

Question Number 199847 by cortano12 last updated on 10/Nov/23 $$\:\mathrm{Find}\:\mathrm{all}\:\mathrm{possible}\:\mathrm{value}\: \\ $$$$\:\frac{\mathrm{a}}{\mathrm{a}+\mathrm{b}+\mathrm{d}\:}\:+\frac{\mathrm{b}}{\mathrm{a}+\mathrm{b}+\mathrm{c}}\:+\:\frac{\mathrm{c}}{\mathrm{b}+\mathrm{c}+\mathrm{d}}+\frac{\mathrm{d}}{\mathrm{a}+\mathrm{c}+\mathrm{d}}\: \\ $$$$\:\mathrm{when}\:\mathrm{a},\mathrm{b},\mathrm{c},\mathrm{d}\:\mathrm{vary}\:\mathrm{over}\:\mathrm{positive} \\ $$$$\:\mathrm{reals}\: \\ $$ Commented by Frix last updated on 10/Nov/23…

Question-198743

Question Number 198743 by mnjuly1970 last updated on 23/Oct/23 Answered by witcher3 last updated on 24/Oct/23 $$\left(\mathrm{A}−\mathrm{I}\right)\left(\mathrm{A}−\mathrm{I}\right)^{−} =\mathrm{I} \\ $$$$=\mathrm{A}\left(\mathrm{A}−\mathrm{I}\right)−\mathrm{I}\left(\mathrm{A}−\mathrm{I}\right)^{−} = \\ $$$$\mathrm{A}\left(\mathrm{A}−\mathrm{I}\right)^{−} −\left(\mathrm{A}−\mathrm{I}\right)^{−} =\mathrm{I}…