Find all values of a, b, and c for which A is symmetric. Use the symbol t as a parameter if needed.

Question

Answer 1

For A to be symmetric: a - 2b + c = 8 (1), 2a + b + c = - 1 (2), a + c = 7 (3).

(2) - (3) gives a + b = - 8, b = - 8 - a, c = 7 - a and substitute in (1), a + 16 + 2a + 7 - a = 8; 2a = -15, a = - 7.5,

b = - 8 + 7.5 = - 0.5; c = 7 + 7.5 = 14.5