Question

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

Answer 1

Let the points be A(1,-1), B(2,1) and C(4,x)

All three points lie on a line. Therefore the slope of AB = slope of BC

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

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

$\Rightarrow 4=x-1$

$Hence,x=5$