[vivekachary1450]

let (x1,y1) and (x2,y2) be the two pointsthen the slope is (y2-y1) / (x2-x1)y=2x+4just put any simple value of x and find out the value of yso say x=0then y = 2*0 + 4 = 4so (0,4) becomes your (x1,y1) now try x=1so y = 2*1 + 4 = 6so (1,6) becomes (x2,y2)so the slope is (6-4) / (1-0) = 2/1 = 2y=-1here the value of y is fixedthat means y1 = -1 y2 = -1 alsoso here slope = (y2-y1) / (x2-x1) = 0 / (x2-x1) = 0(zero slope means it is a flat/ horizontal line, parallel to x-axis)x=3here the value of x is fixedthat means x1 = 3x2 = 3 alsoso here slope = (y2-y1) / (x2-x1) = (y2-y1) / 0 = infinity(infinite slope means it is a vertical line, parallel to y-axis)