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If A -= (3,x,1), B -= (y,-2,2), C -= (2x...

If `A -= (3,x,1), B -= (y,-2,2), C -= (2x,2y,-3)` are the vectors of `triangleABC` and `G -= (2,1,0)` is its centroid, then

A

`x=-1/3, y=-7/3`

B

`x=7/3, y=1/3`

C

`x=1/3, y=7/3`

D

`x=5/3, y=4/3`

Text Solution

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The correct Answer is:
To solve the problem, we need to find the values of \( x \) and \( y \) given the vectors of triangle \( ABC \) and its centroid \( G \). ### Step 1: Understand the Centroid Formula The centroid \( G \) of a triangle with vertices represented by vectors \( A \), \( B \), and \( C \) is given by the formula: \[ G = \left( \frac{x_1 + x_2 + x_3}{3}, \frac{y_1 + y_2 + y_3}{3}, \frac{z_1 + z_2 + z_3}{3} \right) \] where \( (x_1, y_1, z_1) \), \( (x_2, y_2, z_2) \), and \( (x_3, y_3, z_3) \) are the coordinates of points \( A \), \( B \), and \( C \). ### Step 2: Identify Coordinates The coordinates of points \( A \), \( B \), and \( C \) are given as: - \( A = (3, x, 1) \) - \( B = (y, -2, 2) \) - \( C = (2x, 2y, -3) \) The centroid \( G \) is given as \( (2, 1, 0) \). ### Step 3: Set Up the Equations Using the centroid formula, we can set up three equations based on the x, y, and z coordinates. 1. For the x-coordinate: \[ 2 = \frac{3 + y + 2x}{3} \] Multiplying both sides by 3: \[ 6 = 3 + y + 2x \implies y + 2x = 3 \quad \text{(Equation 1)} \] 2. For the y-coordinate: \[ 1 = \frac{x - 2 + 2y}{3} \] Multiplying both sides by 3: \[ 3 = x - 2 + 2y \implies x + 2y = 5 \quad \text{(Equation 2)} \] 3. For the z-coordinate: \[ 0 = \frac{1 + 2 - 3}{3} \] This simplifies to: \[ 0 = 0 \quad \text{(This equation is always true and does not provide any new information)} \] ### Step 4: Solve the System of Equations Now we have a system of two equations: 1. \( y + 2x = 3 \) 2. \( x + 2y = 5 \) We can solve these equations simultaneously. From Equation 1, we can express \( y \) in terms of \( x \): \[ y = 3 - 2x \quad \text{(Substituting into Equation 2)} \] Now substitute \( y \) into Equation 2: \[ x + 2(3 - 2x) = 5 \] Expanding this gives: \[ x + 6 - 4x = 5 \] Combining like terms: \[ -3x + 6 = 5 \] Subtracting 6 from both sides: \[ -3x = -1 \implies x = \frac{1}{3} \] ### Step 5: Find \( y \) Now substitute \( x \) back into Equation 1 to find \( y \): \[ y = 3 - 2\left(\frac{1}{3}\right) = 3 - \frac{2}{3} = \frac{9}{3} - \frac{2}{3} = \frac{7}{3} \] ### Final Values Thus, the values are: \[ x = \frac{1}{3}, \quad y = \frac{7}{3} \]
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Knowledge Check

  • If (x,-6),(2, y) and (2,6) are the vertices of a triangle and (33) and (10/3, 1/3) is its centroid, then the value of x and y respectively

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