1、Lines in the plane,Definition of slopes,The slope of a nonvertical line is the ratio of vertical change(rise) to horizontal(run) between any two points on the line.What is the slope of vertical lines ?The slope of vertical lines are undefined !,What can you conclude from the picture ?,Parallel and p
2、erpendicular lines,In a coordinate plane, two nonvertical lines are parallel if and only if they have the same slope.m1 = m2In a coordinate plane, two nonvertical lines are perpendicular if and only if the product of their slopes is -1m1 m2 = -1,Ex 1. Find slopes of each line. Which lines are parall
3、el?Line l: (-5, 5), (-3,-1)Line m: (-1,5), (0,1)Line n: (3,4), (4, 0),Lines in a plane,f(x) = mx + bm: slope b: y-interceptGraph: a straight lineParallel lines and perpendicular lines,3 forms of linear functions,Slope- intercept form:y = mx+bPoint slope form:y-y1= m(x- x1)Standard form:Ax+by+c = 0,E
4、x 2. Find general form equation for the line through (-3, -8) and (4, -1)Ex 3. The line through (1, 2) with slope m = , find a slope-intercept form equation for the line.,Ex 4. Write an equation of the line k passing through the point (-4, 1) that is perpendicular to the line n with the equation y = 2x 3.What will happen if I change “perpendicular” to “parallel” ?,
