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A-line-passes-through-A-3-0-and-B-0-4-A-variable-line-perpendicular-to-AB-is-drawn-to-cut-x-and-y-axes-at-M-and-N-Find-the-locus-of-the-point-of-intersection-of-the-lines-AN-and-BM-




Question Number 25930 by Tinkutara last updated on 16/Dec/17
A line passes through A(−3, 0) and  B(0, −4). A variable line perpendicular  to AB is drawn to cut x and y-axes at  M and N. Find the locus of the point of  intersection of the lines AN and BM.
AlinepassesthroughA(3,0)andB(0,4).AvariablelineperpendiculartoABisdrawntocutxandyaxesatMandN.FindthelocusofthepointofintersectionofthelinesANandBM.
Answered by ajfour last updated on 16/Dec/17
Answered by ajfour last updated on 16/Dec/17
let M(a,0)  and N(0,b)  slope of MN=−(1/(slope of AB))  ⇒   −(b/a)=(3/4)     ...(i)  slope of AP =slope of AN  ⇒    ((k−0)/(h−(−3)))=(b/3)  ⇒   (k/(h+3))=(b/3)       ....(ii)  slope of BP=slope of BM  ⇒   ((k−(−4))/(h−0))=(4/a)  ⇒  ((k+4)/h)=(4/a)      ....(iii)  (ii)×(iii) gives:      ((k(k+4))/(h(h+3)))=((4b)/(3a))  for locus of P,   h→x   and k→y   ⇒  ((y(y+4))/(x(x+3)))=−1      [using (i)]  or    x^2 +y^2 +3x+4y=0 .
letM(a,0)andN(0,b)slopeofMN=1slopeofABba=34(i)slopeofAP=slopeofANk0h(3)=b3kh+3=b3.(ii)slopeofBP=slopeofBMk(4)h0=4ak+4h=4a.(iii)(ii)×(iii)gives:k(k+4)h(h+3)=4b3aforlocusofP,hxandkyy(y+4)x(x+3)=1[using(i)]orx2+y2+3x+4y=0.
Commented by Tinkutara last updated on 16/Dec/17
Thank you Sir!

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