The sum of the squares of all the roots of the equation is:
- A
- B
- C
- D
The sum of the squares of all the roots of the equation is:
Correct answer:B
Standard Method
Given:
Find: The sum of the squares of all the roots.
Split the equation into cases using the absolute value.
For Case 1, when , we have:
So,
From the solution, the valid root taken is
For Case 2, when , we have:
So,
From the solution, the valid root taken is
Now compute the sum of squares:
Expanding as shown in the solution,
Therefore, the sum of the squares of all the roots is . The correct option is B.
The solution's also displays "The Correct Option is D", but the worked solution concludes , which matches option B. Following the solution working, B is the defensible answer.
Casewise Absolute Value Analysis
Given:
Find: The sum of the squares of all valid roots.
The expression inside the modulus changes sign at
So the equation must be solved in two intervals.
If , then
Hence,
The root retained in the solution is
which satisfies .
If , then
Hence,
The root retained in the solution is
which satisfies .
Now add the squares of these roots:
So the worked result corresponds to option B.
A common mistake is to treat as only for all . This is wrong because absolute value is piecewise-defined. Split into the two cases and before solving.
Students often solve both quadratics completely but forget to check whether each root satisfies the case condition. This is wrong because a root from one branch may be invalid in that interval. Always verify each root against its corresponding inequality.
Another mistake is to add the roots instead of adding their squares. The question asks for , not . First identify the valid roots, then square each one and add.
Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.