Question

Consider the following system of equations:

3x + 2y = 7
-9x -9y = 9
Is 0, -1 a solution to the system of equations? Explain.

(Dropdown 1: Yes, no) because (Dropdown 2: 0, -1 is a solution to only the first equation, 0, -1 is a solution to both equations, 0, -1 is only a solution to the second equation.)

Solve the system of equations using elimination, write your answer in 2-3 sentences and keep it simple.

Answer 1

Dropdown 1: No because Dropdown 2: 0, -1 is only a solution to the second equation.

Using elimination: multiply the first equation by 3 to get 9x + 6y = 21, add this to -9x - 9y = 9 to eliminate x which gives -3y = 30, so y = -10. Substitute y = -10 into 3x + 2y = 7 to get 3x - 20 = 7, so 3x = 27 and x = 9. The solution is (9, -10).