Question

A straight line passes through $(1,2)$ and has the equation $y=2x+k$.Find $k$

Answer 1

If the line passes through $(1,2)$ then $x=1,y=2$ must satisfy the equation $y=2x+k$

$2=2\times 1+k$

$\Rightarrow 2=2+k$

$\therefore k=0$