Question

Use the formula for slope to verify that a horizontal line has a slope of zero and that a vertical has an undefined slope.

I have no idea what to do can some one help explain it to me thanks. :)

Answer 1

The slope of the line through points (x1,y1) and (x2,y2) is given by :
\(\huge m=\frac{y_1-y_2}{x_1-x_2}\)
now horizontal line has equation of the form y=c, here xterm has '0' co-efficient
take any two points on this, say (x1,c),(x2,c)
so put y1 = c and y2 = c in m and tell me what u get.

Answer 2

i'm sorry i don't get what the y = c part ??

Answer 3

i'll draw a horizontal line
can u see that y-co ordinate of every point on that line is same??

Answer 4

yes

Answer 5

that means for any value of x-coordinate , y co-ordinate will be some constant 'c' only.....so we can write its equation as y=c
got this?

Answer 6

i think so the y will stay the same ( constant) meaning y = c ??

Answer 7

yup.
similarly for vertical line , the equation is x=c

Answer 8

i don't get the x=c part ??

Answer 9

can u see that x-co ordinate of every point on that vertical line is same