Find the equations of the medians of a triangle whose sides are given by the equations 3x + 2y + 6 = 0, 2x – 5y + 4 = 0 and x -3y – 6 = 0.
The given equations are
3x + 2y + 6 = 0 …(i)
2x – 5y + 4 = 0 …(ii)
and x – 3y – 6 = 0 …(iii)
Let eq. (i), (ii) and (iii) represents the sides AB, BC and AC respectively of ΔABC
Firstly, we solve the equation (i) and (ii)
3x + 2y + 6 = 0 …(i)
2x – 5y + 4 = 0 …(ii)
Multiplying the eq. (i) by 2 and (ii) by 3, we get
6x + 4y + 12 = 0 …A
6x – 15y + 12 = 0 …B
Subtracting eq. (B) from (A), we get
6x + 4y + 12 – 6x + 15y – 12 = 0
⇒ 19y = 0
⇒ y = 0
Putting the value of y = 0 in eq. (i), we get
3x + 2(0) + 6 = 0
⇒ 3x + 6 = 0
⇒ 3x = -6
⇒ x = -2
Thus, AB and BC intersect at (-2, 0)
Now, we solve eq. (ii) and (iii)
2x – 5y + 4 = 0 …(ii)
and x – 3y – 6 = 0 …(iii)
Multiplying the eq. (iii) by 2, we get
2x – 6y – 12 = 0 …(iv)
Subtracting eq. (iv) from (ii), we get
2x – 5y + 4 – 2x + 6y + 12 = 0
⇒ y + 16 = 0
⇒ y = -16
Putting the value of y = -16 in eq. (ii), we get
2x – 5(-16) + 4 = 0
⇒ 2x + 80 + 4 = 0
⇒ 2x + 84 = 0
⇒ 2x = -84
⇒ x = -42
Thus, BC and AC intersect at (-42, -16)
Now, we solve eq. (iii) and (i)
x – 3y – 6 = 0 …(iii)
3x + 2y + 6 = 0 …(i)
Multiplying the eq. (iii) by 3, we get
3x – 9y – 18 = 0 …(v)
Subtracting eq. (v) from (i), we get
3x + 2y + 6 – 3x + 9y + 18 = 0
⇒ 11y + 24 = 0
⇒ 11y = -24
Putting the value of y in eq. (iii), we get
Let D, E and F be the midpoints of sides BC, CA and AB respectively.
Then the coordinates of D, E and F are
= (-22, -8)
Now, we have to find the equations of Medians AD, BE and CF
The equation of median AD is
⇒ 16x – 59y = 120
The equation of the median BE is
⇒ 58y = 25x + 50
⇒ 25x – 58y + 50 = 0
The equation of median AD is
⇒ 112y + 1792 = 41x + 1722
⇒ 41x – 112y + 1722 – 1792 = 0
⇒ 41x – 112y – 70 = 0