Answer: Choice A, Choice B, Choice C
In other words, it's nearly everything but choice D.
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Step-by-step explanation:
Let's say we select "2" as the thing to fill the blank.
2x+3 = -4x+17
2x+4x = 17-3
6x = 14
x = 14/6
x = 7/3
We get one solution in this case.
The same applies for the values 5 and 7. I'll let you do those steps.
In contrast, if we filled the blank with -4, then,
-4x+3 = -4x+17
-4x+4x = 17-3
0x = 14
0 = 14
We get a contradiction which leads to "no solutions".
Visually, the equations y = -4x+3 and y = -4x+17 are parallel lines that never intersect. We need them to intersect if we want a solution. Recall that parallel lines have equal slopes but different y-intercepts. Both sides have a slope of -4 in this case.
Therefore, the quick rule of thumb is this: if the slopes are not equal, then the linear equation has exactly one solution.