$\left|\begin{array}{ccc} a+b+2c & a & b \\ c & b+c+2a & b \\ c & a & c+a+2b \end{array}\right| = $

If $\begin{vmatrix} ^9C_4 & ^9C_5 & ^{10}C_r \\ ^{10}C_6 & ^{10}C_7 & ^{11}C_{r+2} \\ ^{11}C_8 & ^{11}C_9 & ^{12}C_{r+4} \end{vmatrix} = 0$,then $r$ is equal to:

If $a, b,$ and $c$ are in $A$.$P$.,then the value of $\left|\begin{array}{lll}x+2 & x+3 & x+a \\ x+4 & x+5 & x+b \\ x+6 & x+7 & x+c\end{array}\right|$ is

If $A=\begin{bmatrix} 1 & 1 & 0 \\ 2 & 1 & 5 \\ 1 & 2 & 1 \end{bmatrix}$,then $a_{11} A_{21} + a_{12} A_{22} + a_{13} A_{23} = \dots$

For non-zero $a, b, c$,if $\Delta = \begin{vmatrix} 1 + a & 1 & 1 \\ 1 & 1 + b & 1 \\ 1 & 1 & 1 + c \end{vmatrix} = 0$,then the value of $\frac{1}{a} + \frac{1}{b} + \frac{1}{c} = $

The value of the determinant $\left| \begin{array}{ccc} 1 & a & b + c \\ 1 & b & c + a \\ 1 & c & a + b \end{array} \right|$ is