AMSCO'S Geometry. New York - Rye High School

294 Slopes and Equations of LinesEXAMPLE 1Find the slope of the line that is determined by points (2, 4) and (4, 2).Solution Plot points (2, 4) and (4, 2).Let point (2, 4) be P 1(x 1, y 1) and letpoint (4, 2) be P 2(x 2, y 2).Then, x 12, y 1 4, x 2 4, and y 2 2.g Dyslope of P 1P 2 5 Dx 5 y 2 2 y 1x 2 2 x 15 2 2 44 2 (22)5 22652 1 3Answer2yP 1(2, 4)1 6 O1 11P 2(4, 2)xEXAMPLE 2SolutionThrough point (1, 4), draw the line whose slope is 2 3 2.How to Proceed(1) Graph point A(1, 4).Dy(2) Note that, since slope Dx 523 , when y2 5 232decreases by 3, x increases by 2. Start at pointA(1, 4) and move 3 units downward and 2 unitsto the right to locate point B.(3) Start at B and repeat these movements tolocate point C.(4) Draw a line that passes through points A, B,and C.yA(1, 4)31B2O 1 32xCExercisesWriting About Mathematics1. How is the symbol y read and what is its meaning?2. Brad said that since 0 is the symbol for “nothing,” no slope is the same as zero slope. Doyou agree with Brad? Explain why or why not.