Arturo O. answered 01/11/20
Experienced Physics Teacher for Physics Tutoring
Only ONE system is given in this problem. Evaluate the principal determinant and make sure it is not zero.
D = (1)(4) - (-1)(4) ≠ 0 ⇒ one solution
Add the 2 equations and get
8y = 8
y = 1
Plug this value of y into either equation and get
x = 1
Test the solution.