Question

If the points (1,-1), (2,1) and (4,x) lie on a line, then x is __

Answer 1

All three points lie on a line. Therefore,

$\frac{1-(-1)}{2-1}=\frac{x-1}{4-2}$

$\Rightarrow$ 2/1 = (x-1)/2

$\Rightarrow$ 4 = x-1

Hence, x = 5