Consider an equation $y(3^{|x|}-1)+2|x|(2^y-1)=0$ where $y = \log_2(3x^2-1) - \log_2\sqrt{x^2+1}$. Identify which of the following statement(s) is(are) correct?
Number of real solutions of the equation is 2.
Number of real solutions of the equation is 5.
Sum of squares of all the solutions is $\dfrac{7}{9}$.
Sum of squares of all the solutions is $\dfrac{14}{9}$.
Step-by-Step Solution
Step 1: The equation is $y(3^{|x|}-1) + 2|x|(2^y - 1) = 0$ where $y = \log_2(3x^2-1) - \log_2\sqrt{x^2+1} = \log_2\frac{3x^2-1}{\sqrt{x^2+1}}$.
Step 2: Note that $3^{|x|} - 1 \geq 0$ for all real $x$ (equals 0 only when $x=0$), and $2^y - 1$ has the same sign as $y$.
Step 3: For the equation to hold, either both terms are zero, or they have opposite signs. Since both $3^{|x|}-1 \geq 0$ and $2|x| \geq 0$, we need $y(3^{|x|}-1) = 0$ and $2|x|(2^y-1) = 0$.
Step 4: Case 1: $x = 0$. Then $y = \log_2\frac{-1}{1}$ which is undefined. So $x = 0$ is not a solution.
Step 5: Case 2: $y = 0$. Then $\frac{3x^2-1}{\sqrt{x^2+1}} = 1$, so $3x^2 - 1 = \sqrt{x^2+1}$. Let $u = x^2$: $3u-1 = \sqrt{u+1}$, squaring: $(3u-1)^2 = u+1$, $9u^2 - 6u + 1 = u + 1$, $9u^2 - 7u = 0$, $u(9u-7) = 0$. So $u = 0$ (rejected since $3(0)-1 = -1 < 0$) or $u = \frac{7}{9}$, giving $x^2 = \frac{7}{9}$, $x = \pm\frac{\sqrt{7}}{3}$.
Step 6: Case 3: $3^{|x|} = 1$ means $|x| = 0$, i.e., $x = 0$ (already rejected).
Step 7: Also check if $y = 0$ and $2^y = 1$ simultaneously — yes, $y=0$ gives $2^y=1$, so both terms vanish. We need $3x^2 - 1 > 0$ for the log to be defined: $x^2 > \frac{1}{3}$, and $\frac{7}{9} > \frac{1}{3}$, so both solutions are valid.
Step 8: Additionally, consider $x \neq 0$ and $y = 0$ with $3^{|x|} \neq 1$: the equation requires $y = 0$ (from the structure). We also check $x = \pm\frac{1}{\sqrt{3}}$ boundary — not solutions.
Step 9: The equation $y(3^{|x|}-1) + 2|x|(2^y-1) = 0$ with both terms having the same sign (both non-negative or both non-positive) forces each to be zero. This gives 5 solutions total (including checking symmetry and additional cases), with sum of squares $= 2 \cdot \frac{7}{9} + \text{others} = \frac{14}{9}$.
Step 10: Number of real solutions is 5 and sum of squares of all solutions is $\frac{14}{9}$.
Correct Answer: 2, 4