Question

What is the value of c in this linear system? A) 1 B) -3 C) -1 D) 2

Answer 1

9514 1404 393

Answer:

   B)  -3

Step-by-step explanation:

There are methods for finding only c. Cramer's rule is one of them. It involves finding two determinants and taking their ratio. Here, we choose a more ad hoc approach. It appears that the value of b can be found by combining the last two equations.

  (1/2)(2a +4b -2c) -(a -3b -c) = (1/2)(12) -(-4)

  5b = 10

  b = 2

Now, we can substitute this value into the first two equations. This gives ...

  5a +c = -8

  a - c = 2

Subtracting 5 times the second from the first gives ...

  (5a +c) -5(a -c) = (-8) -5(2)

  6c = -18 . . . . simplify

  c = -3 . . . . . . divide by 6

The value of c is -3.