Math Problem Statement

If det[[a, 1, d], [b, 1, e], [c, 1, f]] = -5 and det[[a, 1, d], [b, 2, e], [c, 3, f]] = 4, then find det[[a, 9, d], [b, 9, e], [c, 9, f]] and det[[a, 0, d], [b, -3, e], [c, -6, f]].

Solution

The problem provides determinants for two 3x3 matrices and asks for the determinants of two additional matrices. Let's go through this step-by-step.

Given Information

  1. det[a1db1ec1f]=5\det \begin{bmatrix} a & 1 & d \\ b & 1 & e \\ c & 1 & f \end{bmatrix} = -5
  2. det[a1db2ec3f]=4\det \begin{bmatrix} a & 1 & d \\ b & 2 & e \\ c & 3 & f \end{bmatrix} = 4

Step 1: First Determinant

To find the determinant of [a9db9ec9f]\begin{bmatrix} a & 9 & d \\ b & 9 & e \\ c & 9 & f \end{bmatrix}:

Observe that each element in the second column is now 9. Since adding a multiple of one row to another row does not change the determinant, we can rewrite this determinant by factoring out 9 from the second column. This effectively adds 8 times the original matrix to the second column without affecting the determinant calculation due to linearity of determinant calculations.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Determinants
Matrix Operations
Linear Algebra

Formulas

Determinant of a 3x3 matrix det[[a, b, c], [d, e, f], [g, h, i]] = a(ei − fh) − b(di − fg) + c(dh − eg)

Theorems

Determinant properties (scaling rows or columns, adding multiples of rows or columns)

Suitable Grade Level

Grade 12 or College-level