how to know if i have to subtract or add in a point slope form? for example the part where it says (x - 1) how would i know if its (x - 1) or (x + 1)

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  rules of signs apply

Step-by-step explanation:

The point-slope form of the equation for a line of slope m through point (h, k) is ...

  y -k = m(x -h)

If the point coordinates are positive, their values show up in the equation with a minus sign.

Example:

  slope 2, point (3, 4)

  y -4 = 2(x -3)

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If a point coordinate is negative, its value shows up in the equation with a plus sign.

Example:

  slope 2, point (-3, 4)

  y -4 = 2(x -(-3)) . . . . fill in the given value

  y -4 = 2(x +3) . . . . . simplify according to sign rules

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The slope keeps its sign.

Example:

  slope -1/2, point (-3, 4)

  y -4 = -1/2(x +3) . . . . we only changed the slope from the previous example

b.-4 units

all you   do is count how many times you move