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Question Number 216139 by mr W last updated on 28/Jan/25

Commented by mr W last updated on 28/Jan/25

find (AP+PQ)_(min) =?

find(AP+PQ)min=?

Commented by Ghisom last updated on 28/Jan/25

seems to be 6

seemstobe6

Commented by mr W last updated on 28/Jan/25

i think too.

ithinktoo.

Answered by mahdipoor last updated on 28/Jan/25

if P =(x,ax^2 ) is fixed ⇒  QP is min when P , Q , B in one line  ⇒ QP=PB−QB=PB−r  s=AP+PQ=  (√(x^2 +(ax^2 −2)^2 ))+(√((x−3)^2 +(ax^2 −6)^2 ))−2  (ds/dx)=0 ⇒ x=3 ⇒ s_(min) =8

ifP=(x,ax2)isfixedQPisminwhenP,Q,BinonelineQP=PBQB=PBrs=AP+PQ=x2+(ax22)2+(x3)2+(ax26)22dsdx=0x=3smin=8

Answered by mr W last updated on 29/Jan/25

Commented by mr W last updated on 29/Jan/25

A=focus of parabola  BQ=r=2  (AP+PQ)_(min) ⇔(AP+PQ+QB)_(min)   (AP+PQ+QB)_(min) =(AP+PB)_(min) =(CP+PB)_(min) =6+2=8  (AP+PQ)_(min) =8−r=6 ✓

A=focusofparabolaBQ=r=2Missing \left or extra \right(AP+PQ+QB)min=(AP+PB)min=(CP+PB)min=6+2=8(AP+PQ)min=8r=6

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