Step-by-step explanation:
step 1. The first equation 4x - y = 5 has a slope of 4. The 2nd equation simply cannot have the same slope for there to be 1 solution.
step 2. -y = 4x + 5. This has a slope of -4 so "yes" it could work.
step 3. y = 4x - 5. "no".
step 4. 2y = 8x - 10. The slope is 8/2 = 4. "no".
step 5. -2y = 8x - 10. The slope is 8/-2 = -4. "yes".
