Answer:
-864
Step-by-step explanation:
The determinant of a matrix product is the product of the determinants. The determinant of a transpose is the same as the determinant of the original. Hence ...

The multiplication of an n×n matrix by a scalar 'a' multiplies its determinant by a^n, so the desired determinant is ...

Step by step:
3 2 1
× 6 4
————————————-
+ 1 2 8 4
+ 1 9 2 6 0
————————————-
= 2 0 5 4 4
The answer of 6and7 irrational number is 6.875