Question

Find the values of r for which the line (r+5)x–(r–1)y+r2+4r−5=0 is 1.parallel to the xx-axis ?
2.parallel to the line 2x−y+4=0 ?
3.parallel to the yy-axis ?
4.perpendicular to the line x−y+32=0?

Answer 1

Given P is equidistant from points A and B

PA=PB .....(1)

and Q is equidistant from points A and B

QA=QB .....(2)

In △PAQ and △PBQ

AP=BP from (1)

AQ=BQ from (2)

PQ=PQ (common)

So, △PAQ≅△PBQ (SSS congruence)

Hence ∠APQ=∠BPQ by CPCT

In △PAC and △PBC

AP=BP from (1)

∠APC=∠BPC from (3)

PC=PC (common)

△PAC≅△PBC (SAS congruence)

∴AC=BC by CPCT

and ∠ACP=∠BCP by CPCT ....(4)

Since, AB is a line segment,

∠ACP+∠BCP=180

∘

Thus, AC=BC and ∠ACP=∠BCP=90

∘

∴,PQ is perpendicular bisector of AB.

Hence proved.