A line with a slope of – 5 passes through the points (6,r) and (7, – 9). What is the value of r?
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comparing the relation given
thus y= -2x +1 to the general equation of a line
where y= mx + c
where m is the gradient and c is the intercept on the y-axis.
from the question, the gradient is -2 and since the line is perpendicular, the gradient is given as
so substituting the value of m in to the equation
=
as the gradient
equation of line is given by
y - y1 = m( x-x1)
from the question y1= -2 and x1=1
substitute them
y-(-2) = 1/2 (x -1)
y+2 =1/2 (x-1)
multiplying through by 2
2 (y+2) = x-1
2y +4 = x-1
2y =x-1-4
2y =x-5
x -2y -5 = 0
therefore the equation for the line is x-2y -5=0