HP 33s - Manual (Page 240)

15–18 Mathematics Programs
Program Instructions:
1. Key in the program routines; press ‡ when done.
2. Press X A to input coefficients of matrix and column vector.
3. Key in coefficient or vector value (A through L) at each prompt and press g .
4. Optional: press X D to compute determinant of 3 × 3 system.
5. Press X I to compute inverse of 3 × 3 matrix.
6. Optional: press X A and repeatedly press g to review the values of the
inverted matrix.
7. Press X M to multiply the inverted matrix by the column vector and to see
the value of X. Press g to see the value of Y, then press g again to see
the value of Z.
8. For a new case, go back to step 2.
Variables Used:
A through I Coefficients of matrix.
J through L Column vector values.
W Scratch variable used to store the determinant.
X through Z Output vector values; also used for scratch.
i Loop–control value (index variable); also used for
scratch.
Remarks:
For 2 × 2 solutions use zero for coefficients C, F, H, G and for L. Use 1 for
coefficient I.
Not all systems of equations have solutions.
Example:
For the system below, compute the inverse and the system solution. Review the
inverted matrix. Invert the matrix again and review the result to make sure that the
original matrix is returned.
23X + 15Y + 17Z = 31
8X + 11Y – 6Z = 17
4X + 15Y + 12Z = 14