Question

If the value of determinant `|[m,2],[-5,7]|`is 31, find the value of m

Answer 1

`|[m,2],[-5,7]|=31`

∴(m × 7) – (–5 × 2) = 31
∴7m – (–10) = 31
∴7m + 10 = 31
∴7m = 21
∴m = 3