Sign in
Please select an account to continue using cracku.in
↓ →
Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
If $$\alpha$$ and $$\beta$$ are the roots of the equation $$2x(2x+1) = 1$$, then $$\beta$$ is equal to:
The given equation is:
$$2x(2x + 1) = 1$$ Expand the left side:
$$4x^2 + 2x = 1$$
$$4x^2 + 2x - 1 = 0$$
For a quadratic equation of the form $$ax^2 + bx + c = 0$$, the sum and product of roots are given by:
From the sum of roots, we can express $$\beta$$ in terms of $$\alpha$$:
$$\beta = -\frac{1}{2} - \alpha$$
We need to check which option matches $$\beta = -\frac{1}{2} - \alpha$$. Let's test the expression in Option B:
$$-2\alpha(\alpha + 1) = -2\alpha^2 - 2\alpha$$
Since $\alpha$ is a root of the equation $$4x^2 + 2x - 1 = 0$$, it must satisfy the equation:
$$4\alpha^2 + 2\alpha - 1 = 0$$
Rearranging to find $$2\alpha^2$$:
$$4\alpha^2 = 1 - 2\alpha$$
$$2\alpha^2 = \frac{1 - 2\alpha}{2} = \frac{1}{2} - \alpha$$
Now, substitute this value of $$2\alpha^2$$ into our expression for Option B:
$$-2\alpha^2 - 2\alpha = -\left( \frac{1}{2} - \alpha \right) - 2\alpha$$
$$= -\frac{1}{2} + \alpha - 2\alpha$$
$$= -\frac{1}{2} - \alpha$$
Since the expression in Option B simplifies exactly to $$-\frac{1}{2} - \alpha$$, which we found to be the value of $$\beta$$:
$$\beta = -2\alpha(\alpha + 1)$$
The correct option is B.
Click on the Email ☝️ to Watch the Video Solution
Create a FREE account and get:
Predict your JEE Main percentile, rank & performance in seconds
Educational materials for JEE preparation
Ask our AI anything
AI can make mistakes. Please verify important information.
AI can make mistakes. Please verify important information.