Question

find the value of x if determinant [3][2] = 9
[6][x]

Answer 1

Hint, determinant of a 2x2 matrix is

\[Det\left[\begin{matrix}a & b \\ c & d\end{matrix}\right] = ad - bc\]

Answer 2

3 x X - 12 = 9

Answer 3

how do we determine X

Answer 4

Well if \(\large 3x - 12= 9\)

How can we use algebra to isolate and solve for 'x'?

Answer 5

Do we divide 3 first to get it to the other side or subtact 12 from 9 first?

Answer 6

Here, you could do either

So lets divide everything by 3 then

\[\large \frac{3x - 12 = 9}{3} \rightarrow x - 4 = 3\]

What now?

Answer 7

so then x just equals 7

Answer 8

Correct

Answer 9

So do we always begin with multiplying/dividing first?