Question:medium

If $m_1$ and $m_2$ are the slopes of the lines represented by $ax^2 + 2hxy + by^2 = 0$ satisfying the condition $16\text{h}^2 = 25\text{ab}$, then

Show Hint

Use $(m_1-m_2)^2$ identity for pair of lines.
Updated On: May 14, 2026
  • $\text{m}_1 = \text{m}_2^2$
  • $m_1 = 4m_2$
  • $|m_1 - m_2| = 2$
  • $\text{m}_1 \text{m}_2 = 1$
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
A homogeneous equation of second degree $ax^2 + 2hxy + by^2 = 0$ represents a pair of straight lines passing through the origin. If their slopes are $m_1$ and $m_2$, there exist direct relations linking the sum and product of these slopes to the coefficients $a, h$, and $b$. We substitute these relations into the given condition to find the specific ratio between the slopes. Step 2: Key Formula or Approach:
1. Sum of slopes: $m_1 + m_2 = -\frac{2h}{b}$. 2. Product of slopes: $m_1 m_2 = \frac{a}{b}$. 3. Express the given condition $16h^2 = 25ab$ entirely in terms of slopes. Step 3: Detailed Explanation:
From the standard formulas, we can express $h$ and $a$ in terms of the slopes and $b$: \[ 2h = -b(m_1 + m_2) \implies h = -\frac{b(m_1 + m_2)}{2} \] \[ a = b(m_1 m_2) \] The given condition is: \[ 16h^2 = 25ab \] Substitute the expressions for $h$ and $a$ into this condition: \[ 16 \left[ -\frac{b(m_1 + m_2)}{2} \right]^2 = 25 [b(m_1 m_2)] b \] Square the term in the brackets: \[ 16 \left[ \frac{b^2(m_1 + m_2)^2}{4} \right] = 25 b^2 (m_1 m_2) \] Simplify the left side ($16/4 = 4$): \[ 4 b^2 (m_1 + m_2)^2 = 25 b^2 (m_1 m_2) \] Assuming $b \neq 0$ (otherwise it's not a proper pair of lines with finite slopes), divide by $b^2$: \[ 4(m_1 + m_2)^2 = 25(m_1 m_2) \] Expand the squared binomial: \[ 4(m_1^2 + 2m_1m_2 + m_2^2) = 25m_1m_2 \] \[ 4m_1^2 + 8m_1m_2 + 4m_2^2 = 25m_1m_2 \] Rearrange into a homogeneous quadratic equation in terms of $m_1$ and $m_2$: \[ 4m_1^2 - 17m_1m_2 + 4m_2^2 = 0 \] To find the relationship ratio, divide the entire equation by $m_2^2$ (assuming $m_2 \neq 0$): \[ 4\left(\frac{m_1}{m_2}\right)^2 - 17\left(\frac{m_1}{m_2}\right) + 4 = 0 \] Let the ratio $r = \frac{m_1}{m_2}$. The equation becomes: \[ 4r^2 - 17r + 4 = 0 \] Factor the quadratic equation: \[ 4r^2 - 16r - r + 4 = 0 \] \[ 4r(r - 4) - 1(r - 4) = 0 \] \[ (4r - 1)(r - 4) = 0 \] So, $r = \frac{1}{4}$ or $r = 4$. This means $\frac{m_1}{m_2} = \frac{1}{4} \implies 4m_1 = m_2$, OR $\frac{m_1}{m_2} = 4 \implies m_1 = 4m_2$. Looking at the options, $m_1 = 4m_2$ is present. Since the naming of slopes is arbitrary, both relations denote the same physical pair of lines where one slope is four times the other. Step 4: Final Answer:
The relation is $m_1 = 4m_2$.
Was this answer helpful?
0