HP50g or other: U. of Houston calc exams

[CR Haeger]

Here is how I worked this problem:

19. Give the value of "a" for which the system below has a solution (Calculator Exam – 2015)
2x -3y = 6 - 7a
-3x + 5y = 7+ 2a
7x +11y = 4 - 6a

Rearranged to a 3x3 linear system

2x -3y +7a = 6
-3x + 5y -2a = 7
7x +11y +6a= 4

I used a TI36x [sys solv] and obtained

x = -287/128 (corrected the sign)
y = 101/128
a = 235/128 shown as z in output

To check, used [matrix] to create [3x3 coeff] and [3x1, x-z coeff] matrices then multiplied them, giving [6 7 4] 1x3 array.

These exam questions are interesting to try to solve on the TI36x.