Question

------| 1 0 0 |
If A= | 2 3 4| And det A = 45 then find x.
-------| 5 -6 x|

Answer 1

Answer:

det(A)=

∣

∣

∣

∣

∣

∣

∣

∣

1

2

5

0

3

−6

0

4

x

∣

∣

∣

∣

∣

∣

∣

∣

=1(3x+24), expand along first row

⇒45=3x+24

⇒3x=45−24=21

∴x=7