Question

the line joining A(-1,-2) and B (5,6) is perpendicular to C (4,2) and D(0,y) . find y​

Answer 1

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Answer 2

Slope (m) = (y2 - y1) / (x2 - x1)

Therefore ,

slope of the line A(-1,-2) and B (5,6) is

m1 = (6 + 2)/(-1 - 5)

m1 = 8/(-6)

m1 = -4/3

slope of the line C (4,2) and D(0,y) is

m2 = (y - 2)/(0 - 4)

m2 = (y - 2)/(-4)

m2 = -(y - 2)/4

m2 = (2 - y)/4

Since , if 2 lines are perpendicular to each other then

m1 × m2 = -1

Thus，

-4/3 × (2 - y)/4 = -1

(-8 + 4y)/12 = -1

-8 + 4y = -12

4y = -4

y = -1

Thus , y = -1

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