If $\begin{bmatrix}ab&cd\\a+c&b+d\end{bmatrix}=\begin{bmatrix}2&-3\\4&1\end{bmatrix}$ where a, b,c,d are integers, then which of the following are true? |
(A), (B) and (C) only (A), (C) and (D) only (B) and (C) only (B), (C) and (D) only |
(A), (C) and (D) only |
The correct answer is Option (2) → (A), (C) and (D) only $\begin{pmatrix}ab & cd\\ a+c & b+d\end{pmatrix} = \begin{pmatrix}2 & -3\\ 4 & 1\end{pmatrix}$ $ab=2,\quad cd=-3,\quad a+c=4,\quad b+d=1$ $ab=2$ $a=1,\; b=2$ $a=2,\; b=1$ $a=-1,\; b=-2$ $a=-2,\; b=-1$ Using $a+c=4$ $c=4-a$ Using $b+d=1$ $d=1-b$ Using $cd=-3$ $(4-a)(1-b)=-3$ Substitute possible $(a,b)$: $a=2,\; b=1$ $c=4-2=2,\quad d=1-1=0$ $cd=0\neq-3$ $a=1,\; b=2$ $c=4-1=3,\quad d=1-2=-1$ $cd=3(-1)=-3$ ✓ Thus $a=1,\; b=2,\; c=3,\; d=-1$ $a+d=1+(-1)=0$ $b+d=2+(-1)=1$ $c+d=3+(-1)=2$ Correct options: A, C, D |