SOLUTION: the straight line which passes through the points A(1,2) and B(3,a) is perpendicular to the line, y-2x+8=0. calculate the value of "a" How do I work this out? Please help.

Question 893584: the straight line which passes through the points A(1,2) and B(3,a) is perpendicular to the line,
y-2x+8=0. calculate the value of "a"
How do I work this out? Please help.
Answer by josgarithmetic(39618) (Show Source): You can put this solution on YOUR website!
the given line.
, given line in slope-intercept form.
Slope is 2.

The slope for a line perpendicular to the given line will be .
The slopes of two perpendicular lines will be negative reciprocals.

Formula for slope using the two points of the line perpendicular to the given line:

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