Question

HELP!! Find the value of… (picture)

Answer 1

C. 94

Explanation:

|A| =
`\left[\begin{array}{ccc}a&b&c\\d&e&f\\g&h&i\end{array}\right]`

det(A) = a *
`\left[\begin{array}{ccc}e&f\\h&i\\\end{array}\right]` - b *
`\left[\begin{array}{ccc}d&f\\g&i\\\end{array}\right]` + c *
`\left[\begin{array}{ccc}d&e\\g&h\\\end{array}\right]`

OR

det(A) = aei - afh - bdi + bfg + cdh - ceg

|A| =
`\left[\begin{array}{ccc}-2&-2&-5\\2&7&-3\\8&9&9\end{array}\right]`

det(A) = -2 *
`\left[\begin{array}{ccc}7&-3\\9&9\\\end{array}\right]` - (-2) *
`\left[\begin{array}{ccc}2&-3\\8&9\\\end{array}\right]` + (-5) *
`\left[\begin{array}{ccc}2&7\\8&9\\\end{array}\right]`

OR

det(A) = (-2)(7)(9) - (-2)(-3)(9) - (-2)(2)(9) + (-2)(-3)(8) + (-5)(2)(9) - (-5)(7)(8)

det(A) = 94