12 multiple-choice questions, progressively harder.
One slope triangle on a nonvertical line has rise 2 and run 5. Another has rise 6 and run 15. Which explanation establishes that the slopes agree?
Solution
Correct answer: B
Each triangle has a right angle and the same acute angle with a horizontal line, so AA gives similarity. Their leg ratios agree.
A nonvertical line through (−2,7)(-2,7)(−2,7) has slope −3/5-3/5−3/5. Which equation describes it?
Correct answer: D
Point-slope form uses the given point and direction.
Substituting (−2,7)(-2,7)(−2,7) makes both sides zero, and the coefficient is the required slope.
Compare the two equations.
What is their relationship?
Correct answer: A
Dividing the second equation by 7 gives
It matches the first equation, so the lines coincide.
The equations
and
describe which relationship?
Correct answer: C
The equations reduce to two different fixed first coordinates.
The lines are distinct and vertical, so they are parallel. Neither has a slope number.
A right triangle along a line has run 5 right and rise 2 up. What is the slope of its image after a counterclockwise quarter-turn?
The run of 5 turns upward, and the rise of 2 turns left. The new signed run is −2-2−2 and the new rise is 5.
Two slanted lines have slopes −4/7-4/7−4/7 and 7/47/47/4. Which calculation establishes their perpendicularity?
Both slopes exist and are nonzero. Their product is
The perpendicular criterion therefore applies.
Through P=(−6,3)P=(-6,3)P=(−6,3), which line is perpendicular to the horizontal line y=−8y=-8y=−8?
A perpendicular to a horizontal line is vertical. It fixes the first coordinate of PPP.
The slope-product rule is unavailable for this vertical line.
Find the perpendicular bisector of a segment with endpoints (−7,−2)(-7,-2)(−7,−2) and (3,−2)(3,-2)(3,−2).
The midpoint is (−2,−2)(-2,-2)(−2,−2). The segment is horizontal, so its perpendicular bisector is vertical through that midpoint.
Triangle ABCABCABC has vertices
Which is its median line from AAA?
The midpoint of BCBCBC is (5,−1)(5,-1)(5,−1). The slope from AAA to that midpoint is
Through AAA this gives
In a triangle, side BCBCBC lies on the vertical line x=4x=4x=4, and A=(−2,6)A=(-2,6)A=(−2,6). What is the altitude line from AAA?
The opposite side is vertical, so its perpendicular through AAA is horizontal.
This line passes through AAA and meets the full line of BCBCBC at a right angle.
Find the intersection of the perpendicular bisector x=−3x=-3x=−3 and the median line y=2x+8y=2x+8y=2x+8.
Substitute the fixed first coordinate into the second equation.
The intersection is (−3,2)(-3,2)(−3,2).
Two nonvertical line equations have the same slope and contain the same point. Which conclusion is justified?
The common slope mmm and common point (a,b)(a,b)(a,b) give both equations the same point-slope form.
A point and a slope fix one line, so this is the coincident case.
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