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Two perpendicular lines PQ and QR intersect at (1, -1). I...

Two perpendicular lines PQ and QR intersect at (1, -1). If the equation of PQ is x - 2y + 4 = 0, find the equation of QR

A.

x + 2y - 1= -0

B.

2x + y - 3 = 0

C.

x - 2y - 3 = 0

D.

2x + y - 1 = 0

Correct answer is D

Line PQ : x - 2y + 4 = 0

2y = x + 4 y=x2+2

Slope = 12

Slope of the perpendicular line QR: 112=2

Line QR: y=mx+b

y=2x+b 

Point of intersection: (1, -1)

1=2(1)+bb=1+2=1

y=2x+1y+2x1=0

QR:2x+y1=0