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Question

In which ratio the point (-3, p) divides the line segment joining the points (-5, -4) and (-2, 3)?

The correct answer is

2 : 1

Finding the Ratio for Line Segment Division

This question asks us to determine the ratio in which a specific point, denoted as P(-3, p), divides the line segment formed by joining two other given points, A(-5, -4) and B(-2, 3).

Understanding the Section Formula

To solve this, we utilize the section formula from coordinate geometry. The section formula helps us find the coordinates of a point that divides a line segment internally in a given ratio.

If a point $P(x, y)$ divides the line segment joining points $A(x_1, y_1)$ and $B(x_2, y_2)$ in the ratio $m:n$, the coordinates of P are given by:

$$ x = \frac{mx_2 + nx_1}{m+n} $$ $$ y = \frac{my_2 + ny_1}{m+n} $$

In this problem, we are given:

  • Point $A(x_1, y_1) = (-5, -4)$
  • Point $B(x_2, y_2) = (-2, 3)$
  • The dividing point $P(x, y) = (-3, p)$
  • The ratio is $m:n$ (which we need to find).

Applying the Formula to Find the Ratio

We can use either the x-coordinate or the y-coordinate of the point P to find the ratio $m:n$. Since the x-coordinate of P is given as -3, let's use the formula for the x-coordinate:

$$ x = \frac{mx_2 + nx_1}{m+n} $$

Substitute the known values:

$$ -3 = \frac{m(-2) + n(-5)}{m+n} $$

Now, we solve this equation for the ratio $m:n$. Multiply both sides by $(m+n)$:

$$ -3(m+n) = m(-2) + n(-5) $$ $$ -3m - 3n = -2m - 5n $$

Rearrange the terms to group m and n together:

$$ -3m + 2m = -5n + 3n $$ $$ -m = -2n $$

To find the ratio $m:n$, we can divide both sides by $-n$ (assuming $n \neq 0$):

$$ \frac{-m}{-n} = \frac{-2n}{-n} $$ $$ \frac{m}{n} = 2 $$

This can be written as a ratio:

$$ m:n = 2:1 $$

Conclusion

Therefore, the point (-3, p) divides the line segment joining the points (-5, -4) and (-2, 3) in the ratio 2 : 1. Notice that we didn't need the value of 'p' to determine this ratio.

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Important Questions from Co-ordinate Geometry

  1. In which quadrant both abscissa and ordinate are negative?

  2. Find the slope of the line joining the points (3, -4) and (5, 2).

  3. A1 (x1, y1), A2 (x2, y2), A3 (x3, y3) and A4 (x4, y4) are 4 points, p1 divides A1A2 in the ratio 1 ∶ 1, p2 divides P1A3 in the ratio 1 ∶ 2, P3 divides p2A4 in the ratio 1 ∶ 3. Then the coordinates of p3 are:

  4. If (3, 2) are coordinates of the centroid of a triangle, whose vertices are (0, 4), (-2, 0) and (p, 2), then find the value of p.

  5. The graph of the given line 3x - 4y = 0 will pass through which of the following points?
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