f(x)=ax+bf(x)=ax+b
a=y2−y1x2−x1a=(y_2-y_1)/(x_2-x_1)
b = y 2 − x 2 ⋅ a b=y_2−x_2*a eller b = y 1 − x 1 ⋅ a b=y_1−x_1*a
