Point slope form: can't figure out example in index

[bananagirl5]

On the example in the index for point slope form they give you a graph with points (-1,0) and they plotted the points. What i don't understand is when they supplied the answer the 1 was positive. Is that correct? This is how they wrote it y-0=2(x+1) I also cannot figure out how they got the slope.

 

[skeeter]

the point-slope form is ...

y - y₁ = m(x - x₁)

the given point is (x₁ , y₁) = (-1, 0)

substitute ...

y - 0 = m[x - (-1)] = m(x + 1)

see where the x+1 came from?

as far as the slope goes ... either it is given or there is another given point on the line so that it may be calculated.