Line M passes through the points (-5, 9) and (-1, 9) which is true of line M? A: line M is a vertical line with an undefined slop
B: line M is a vertical line with a slope of zero
C: Line M is a horizontal line with an undefined slope
D: Line M is a horizontal line with a slope of zero

D: Line M is a horizontal like with a slope of zero

Step-by-step explanation:

A vertical line would have the same x-value for coordinates but different y-values. It would also have an undefined slope.

Therefore, we can rule out A and B.

A horizontal line always has different x-values but the same y-value. It would also have a slope of zero.

Therefore, C is wrong and D is our answer.

Let's first find the slope of the line.

We can do this using the slope formula.

m = y₂ - y1 / x₂ - x₁

We take the second y minus the first y over the second x minus the first x.

So we have 9 - 9 / -1 - (-5).

So we have 0 / 4 which is 0.

So the slope of our line is zero.

We can eliminate any choices that say the slope is undefined.

Now, if we have a slope of zero, the line is flat or horizontal.

So we know line M has to be a horizontal or flat line with a slope of zero.

So our answer is D.

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step-by-step explanation: