The sum of the squares of the roots of and the squares of the roots of , is:
- A
- B
- C
- D
The sum of the squares of the roots of and the squares of the roots of , is:
Correct answer:C
Standard Method
Given: We need the sum of the squares of the roots of and .
Find: The total of the sums of squares of the roots of both equations.
For the first equation, let
Then
Factoring,
So or . Since , we discard .
Hence,
So,
Therefore the roots are
Their sum of squares is
For the second equation,
so
Now split into cases.
If , then , giving
that is,
From the solution working, is taken as a root.
If , then , giving
that is,
From the solution working, is taken as a root.
Thus the roots used for the second equation are and , and their sum of squares is
Finally,
Therefore, the correct option is C.
Case-wise Working
Given: The equations are and .
Find: The total sum of the squares of all roots obtained from these two equations.
For
put
Then
which factors as
So only is valid.
Hence,
Therefore,
So the first contribution is
For
consider modulus cases.
Case 1:
So,
which becomes
The extracted solution states that is a root in this case.
Case 2:
So,
which becomes
The extracted solution states that is a root in this case.
Hence the second contribution is
Adding both parts,
Therefore, the required sum is , so the correct option is C.
Note: The second approach shown in the source solution discusses a different equation, but the primary solution and stated correct option both support option C for the given question.
Treating as an unrestricted variable. This is wrong because modulus is always non-negative, so values like must be rejected. Always impose after substitution.
Not splitting into separate cases. This is wrong because has different forms for and . Solve each case with its own condition and then verify the obtained roots.
Forgetting that the question asks for the sum of the squares of the roots, not the sum of the roots. After finding the roots, compute expressions like before combining the two parts.
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