Answer:
k = -2
Explanation:
1. Substitute the point (2,-1) into the given equation 5x+ky=12. The first number is 2, the x-value. The second number is -1, the y-value.
5x + ky = 12
5(2) + k(-1) = 12
2. Simplify
5(2) + k(-1) = 12
10 + (-k) = 12
10 - k = 12
2. Isolate k
10 - k = 12
-k = 12-10
-k = 2 <= here multiply both sides by (-1)
k = -2