Question

if pqr are collinear
then pq+qr=pr
​

Answer 1

let's assume

pq+qr≠ pr

if it's not equal it will be either :—

pq+qr<pr

this is not possible as either the sum will be greater then pr or equal to only.

because pr is a line and then q can either be a point on pr or not on pr. when it is a point on pr the sum will be equal and when not the sum will be greater{as it will form a triangle}.

or

pq+qr>pr

if this is true then pqr will be a triangle hence the points will not be collinear. but it's given that they are so, this leads to contradiction and hence,

pq+qr=pr

Hope it Helps You

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