Q. 115.0( 1 Vote )

# The line joining the points A (0, 5) and B (4, 2) is perpendicular to the line joining the points C (–1, –2) and D (5, b). Find the value of b.

Line joining points A (0, 5) and B (4, 2) IA parallel to the line joining the points C (–1, –2) and D (5, b)

The two lines are perpendicular only if the multiplication of their slope is equal to 1.

(Slope of AB) × (Slope of CD) = 1

Slope of line passing through (x1, y1) and (x2, y2) is Slope of AB is:

A (0, 5) and B (4, 2)  Slope of CD is:

C (–1, –2) and D (5, b)  The two lines are perpendicular only if the multiplication of their slope is equal to 1.

(Slope of AB) × (Slope of CD) = –1   –b – 2 = –1 × 8

–b – 2 = –8

–b = –8 + 2

– b = – 6

b = 6

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