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

Question

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

johnweldon1993 · Answer

Hint, determinant of a 2x2 matrix is

$$Det\left[\begin{matrix}a & b \ c & d\end{matrix}\right] = ad - bc$$

dehelloo · Answer

3 x X - 12 = 9

dehelloo · Answer

how do we determine X

johnweldon1993 · Answer

Well if $\large 3x - 12= 9$

How can we use algebra to isolate and solve for 'x'?

dehelloo · Answer

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

johnweldon1993 · Answer

Here, you could do either

So lets divide everything by 3 then

$$\large \frac{3x - 12 = 9}{3} \rightarrow x - 4 = 3$$

What now?

dehelloo · Answer

so then x just equals 7

johnweldon1993 · Answer

Correct

dehelloo · Answer

So do we always begin with multiplying/dividing first?