Browse Questions

# If $\begin{vmatrix} 3x & 7 \\ 2 & 4 \end{vmatrix}$= 10, find x.

Toolbox:
• The determinant value of a $2\times 2$ matrix is $|A|=a_{11}\times a_{22}-a_{21}\times a_{12}$
$\begin{vmatrix}3x & 7\\2 & 4\end{vmatrix}$=10
Now let us evaluate the value of the determinant
$3x\times 4-7\times 2=10.$
12x-14=10.
12x=10+14
12x=24
x=$\frac{24}{12}=2$
Hence the value of x=2.