Question 153151
1. How do we write the equation of a horizontal line? What would be an example?
Ans: y = 3 is a horizontal line.
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2. How do we write the equation of a vertical line? What would be an example?
Ans: x = 3 is a vertical line.
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3. The points (3, 9), (5, 13), (15, 33), (34, 71), (678, 1359), and (1234, 2471) all lie on line M.
The points (3, -9), (5, -11), (15, -21), (34, -40), (678, -684), and (1234, -1240) all lie on line N.
a. Form the equations of both the lines. Show your work.
Line M: 
slope = (13-9)/(5-2) = 4/2 = 2
Intercept: 9 = 2*3+b
b = 3
Equation: y = 2x + 3
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Line N: 
slope = (-11--9)/(5-3) = -2/2 = -1
Intercept: -9 = -1*3 + b 
b = -6
Equation: y = -x-6
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b. What are the co-ordinates of the point of intersection of lines M and N?
2x+3 = -x-6
3x = -9
x = -3
Substitute to solve for "y":
y = 2(-3)+3 = -3
Point of intersection (-3,-3)
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c. Write the co-ordinates of the intersections of lines M and N with the x-axis.
M Equation: y = 2x + 3
Let y = 0 
0 = 2x + 3
x = -3/2
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N Equation:y = -x-6
Let y = 0
0 = -x-6
x = -6
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d. Write the co-ordinates of the intersection of lines M and N with the y-axis.
Let x = 0
M Equation: y = 2x + 3
y-intercept y = 3
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N Equation: y = -x-6
y-intercept y = -6
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Cheers,
Stan H.