Two points A (-2, 9) and B (4, 8) lie on a line l. (i) Find the slope of the line l. (2)marks (ii) Find the coordinates of the midpoint of the points A and B (iii) Find the distance between points A and B. (i). A line “t” is parallel to 3y = 6x + 9. Find the slope of this line “t”. (ii) Another line “r” is perpendicular to the line 3y = 6x + 9. Find the gradient of the line “r”.

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Answer:

Question 1:

The coordinates are A(-2,9) and B(4,8)

(i) Slope = [tex]\frac{rise}{run}[/tex]

Slope = [tex]\frac{y2-y1}{x2-x1}[/tex]

Slope = [tex]\frac{8-9}{4+2}[/tex]

Slope = [tex]\frac{-1}{6}[/tex]

(ii) M(x,y) = [tex](\frac{x1+x2}{2} , \frac{y1+y2}{2} )[/tex]

=> M(x,y) = [tex](\frac{-2+4}{2}, \frac{9+8}{2})[/tex]

=> M(x,y) = [tex](\frac{2}{2} , \frac{17}{2} )[/tex]

=> M(x+y) = (1 , 8.5)

(iii) Distance Formula = [tex]\sqrt{(x2-x1)^2+(y2-y1)^2}[/tex]

D = [tex]\sqrt{(4+2)^2+(8-9)^2}[/tex]

D = [tex]\sqrt{(6)^2+(-1)^2}[/tex]

D = [tex]\sqrt{36+1}[/tex]

D = [tex]\sqrt{37 }[/tex] units

Question 2:

(i) The given equation is:

=> 3y = 6x+9

=> 3y = 3(2x+3)

Dividing both sides by 3

=> y = 2x+3

Where Slope = m = 2 and y-intercept = b = 3

Parallel lines have equal slopes

=> So,  Slope of line "t" = 2

(ii) Line 3y = 6x+9 has a slope of 2

=> Perpendicular lines have a slope of negative reciprocal such that multiplying their slopes will give -1

=> Gradient of line "r" = -1/2