Question

The equations of two sides AB and AC of a triangle ABC are $4x + y = 14$ and $3x - 2y = 5$, respectively. The point $\left(2, -\frac{4}{3}\right)$ divides the third side BC internally in the ratio 2 : 1. The equation of the side BC is:

• A. x – 6y – 10 = 0
• B. x – 3y – 6 = 0
• C. x + 3y + 2 = 0
• D. x + 6y + 6 = 0

Answer 1

The Correct Option is C

Given:
The given equations are:
\[ AB : 4x + y = 14, \quad AC : 3x - 2y = 5. \]
Coordinates of \( B \) and \( C \)
The coordinates of \( B \) on \( AB \):
\[ B(x_1, y_1) \quad \text{where } y_1 = 14 - 4x_1. \]
The coordinates of \( C \) on \( AC \):
\[ C(x_2, y_2) \quad \text{where } y_2 = \frac{3x_2 - 5}{2}. \]
Use Section Formula
The point \( P(2, -\frac{4}{3}) \) divides \( BC \) in the ratio \( 2 : 1 \). Using the section formula:
\[ x_p = \frac{2x_2 + x_1}{3}, \quad y_p = \frac{2y_2 + y_1}{3}. \]
Substitute \( x_p = 2 \) and \( y_p = -\frac{4}{3} \) into these equations.
Solve for \( x_1 \) and \( x_2 \)
For \( x_p = 2 \):
\[ 2 = \frac{2x_2 + x_1}{3}. \]
Rearrange:
\[ 6 = 2x_2 + x_1 \quad \implies \quad x_1 = 6 - 2x_2. \]
For \( y_p = -\frac{4}{3} \):
\[ -\frac{4}{3} = \frac{2y_2 + y_1}{3}. \]
Substitute \( y_1 = 14 - 4x_1 \) and \( y_2 = \frac{3x_2 - 5}{2} \):
\[ -\frac{4}{3} = \frac{2\left(\frac{3x_2 - 5}{2}\right) + (14 - 4x_1)}{3}. \]
Simplify:
\[ -\frac{4}{3} = \frac{3x_2 - 5 + 14 - 4x_1}{3}. \]
Multiply through by 3:
\[ -4 = 3x_2 - 5 + 14 - 4x_1. \]
Combine terms:
\[ -4 = 3x_2 + 9 - 4x_1 \quad \implies \quad 3x_2 - 4x_1 = -13. \]
Substitute \( x_1 = 6 - 2x_2 \) into \( 3x_2 - 4x_1 = -13 \):
\[ 3x_2 - 4(6 - 2x_2) = -13. \]
Simplify:
\[ 3x_2 - 24 + 8x_2 = -13 \quad \implies \quad 11x_2 = 11 \quad \implies \quad x_2 = 1. \]
Substitute \( x_2 = 1 \) into \( x_1 = 6 - 2x_2 \):
\[ x_1 = 6 - 2(1) = 4. \]
--- Step 4: Solve for \( y_1 \) and \( y_2 \)
Substitute \( x_1 = 4 \) into \( y_1 = 14 - 4x_1 \):
\[ y_1 = 14 - 4(4) = -2. \]
Substitute \( x_2 = 1 \) into \( y_2 = \frac{3x_2 - 5}{2} \):
\[ y_2 = \frac{3(1) - 5}{2} = \frac{-2}{2} = -1. \]
Thus, \( B(4, -2) \) and \( C(1, -1) \).
Slope of \( BC \)
The slope of \( BC \) is:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{-1 - (-2)}{1 - 4} = \frac{1}{-3} = -\frac{1}{3}. \]
Equation of \( BC \)
Using the point-slope form at \( B(4, -2) \):
\[ y - (-2) = -\frac{1}{3}(x - 4). \]
Simplify:
\[ y + 2 = -\frac{1}{3}x + \frac{4}{3}. \]
Multiply through by 3:
\[ 3y + 6 = -x + 4 \quad \implies \quad x + 3y + 2 = 0. \]
Final Answer:
\[ \boxed{x + 3y + 2 = 0.} \]