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How to find the determinant and inverse of a matrix on a TI-84 Plus CE, TI-84 Plus or TI-83 Plus

By E-Code · updated

Type the matrix into [A] (2nd MATRIX, ▶ ▶ EDIT, ENTER), then on the home screen press 2nd MATRIX, ▶ to MATH, 1 for det(, 2nd MATRIX 1 for [A], ) and ENTER. For the inverse paste [A] (2nd MATRIX 1), press x⁻¹ and ENTER.

Step by step

  1. Open MATRIX. 2nd X⁻¹ Press 2nd, then x⁻¹. MATRIX (above x⁻¹) has three tabs: NAMES MATH EDIT.
  2. Go to EDIT. ▶ ▶ Press ▶ twice to reach EDIT.
  3. Edit matrix [A]. ENTER Press ENTER to edit [A]. First it asks for its size: rows × columns.
  4. Make it 2 × 2. 2 ENTER 2 ENTER Type 2 ENTER 2 ENTER for 2 rows and 2 columns.
  5. Type the numbers. 4 ENTER 7 ENTER 2 ENTER 6 ENTER Type each number and ENTER, row by row: 4, 7, then 2, 6.
  6. Go back home. 2nd MODE Press 2nd, then MODE (QUIT). [A] is kept.
  7. MATRIX again. 2nd X⁻¹ Press 2nd, then x⁻¹.
  8. The MATH tab. ▶ Press ▶ once for MATH, the matrix tools. Item 1 is det(, the determinant.
  9. Pick det(. 1 Press 1. det( is pasted on the home screen.
  10. Open the matrix names. 2nd X⁻¹ Press 2nd, then x⁻¹. The NAMES tab lists the matrices.
  11. Pick [A]. 1 Press 1 for [A].
  12. Get the determinant. ) ENTER Press ) and ENTER.
  13. The names again. 2nd X⁻¹ Now the inverse. Press 2nd, then x⁻¹.
  14. Pick [A]. 1 Press 1 for [A].
  15. Raise it to −1. X⁻¹ Press x⁻¹. On a matrix it means the inverse.
  16. Get the inverse. ENTER Press ENTER.
  17. Read both. det([A]) = 4·6 − 7·2 = 10, and [A]⁻¹ = [[.6 −.7][−.2 .4]]. A determinant of 0 means there's no inverse: ERR:SINGULAR MAT.

What the screen shows

det([A]) = 4·6 − 7·2 = 10, and [A]⁻¹ = [[.6 −.7][−.2 .4]]. A determinant of 0 means there's no inverse: ERR:SINGULAR MAT.

Look for [-.2 .4]] on the screen.

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