Question

Find the equation of the line that passes through points (3,5) and (-6,2). Write the equation in slope intercept form.

Answer 1

1)  gradient of line = Δ y ÷ Δ x
                              = (5 -2) ÷ (3 - (-6))
                              = ¹/₃
   
     using the point-slope form (y-y₁) = m(x-x₁)
     using (3,5)
           (y - 5) = ¹/₃ (x -3)
             y - 5  = ¹/₃x - 1
        ⇒        y =   ¹/₃ x  + 4  [OPTION D]


2)        y =  2x  +  5  .... (1)
           y = ¹/₂ x  + 6  .... (2)
       
         by substituting y in (1) for y in (2)

           2x  +  5 = ¹/₂ x  + 6 
                 ³/₂ x = 1
                      x = ²/₃

        by substituting found x (2)

            y = ¹/₂ (²/₃)  + 6
            y = ¹⁹/₃

∴ common point is (²/₃ , ¹⁹/₃)  thus answer is FALSE [OPTION B]


3) Yes [OPTION A]
     This is because the both have a gradient of 5 and if they have the same gradient then that means that the two lines are parallel to each other.

4) No [OPTION B]
       Two lines are perpendicular if their gradients multiply to give - 1 and as such one is the negative reciprocal of the other.  Since both gradients are ¹/₂ then they are actually parallel and not perpendicular.