What is the equation of the line passing through (21,4) and (18,-2)?

1 Answer
May 14, 2018

y=2x-38

Explanation:

The equation of a straight line is y = mx + c . Where x is gradient and c is the y intercept.

m = (deltay)/(deltax)
(the symbol for delta is wrong. It is actually a triangle. Delta means "change in".)
So in our case:
m = (4 - -2)/(21-18) = 6/3 = 2
You can then substitute 2 into the equation: y = 2x +c

You can then find out what c substituting one of the co-ordinates in.
y=2x+c --> 4=21*2+c = 42 + c
If you take away 42 from both sides c = -38

So the answer is y=2x-38