let m_(AB), m_(AC) and m_(BC)mAB,mACandmBC be the slope of AB, AC and BCAB,ACandBC, respectively.
a) m_(AB)=(4-1)/(-1-1)=-3/2mAB=4−1−1−1=−32
given m_(AB)=-3m, => -3m=-3/2, => m=1/2mAB=−3m,⇒−3m=−32,⇒m=12
=> m_(AC)=3m=3/2, and m_(BC)=m=1/2⇒mAC=3m=32,andmBC=m=12
b) let (x,y)(x,y) be the coordinates of CC,
m_(AC)=3/2=(y-1)/(x-1)mAC=32=y−1x−1,
=> 3x-2y-1=0 ----- Eq(1)⇒3x−2y−1=0−−−−−Eq(1)
similarly, m_(BC)=1/2=(y-4)/(x+1)mBC=12=y−4x+1,
=> x-2y+9=0 ----- Eq(2)⇒x−2y+9=0−−−−−Eq(2)
Eq(1)-Eq(2), => 2x-10=0Eq(1)−Eq(2),⇒2x−10=0,
=> x=5⇒x=5, substituting x=5x=5 in Eq(1) or Eq(2), we get,
y=7y=7,
=>⇒ coordinates of C=(5,7)C=(5,7)