The sum of all the roots of the equation , is:
- A
- B
- C
- D
The sum of all the roots of the equation , is:
Correct answer:C
Standard Method
Given: The equation is . We have to find the sum of all its roots.
Find: The sum of all values of satisfying the equation.
Use the substitution . Since , the equation becomes
Factoring,
So,
Now substitute back:
which gives
and
Also,
which gives
and
Thus the roots are . Their sum is
Therefore, the sum of all the roots is , so the correct option is C.
Using absolute value substitution
The key observation is that the equation contains both and . Writing converts it into a quadratic in one variable.
Then solve
by factorization to get and .
For each value of , solve the corresponding absolute value equation:
Adding all roots,
Hence, the required sum is .
A common mistake is to treat as giving only . This is wrong because an absolute value equation gives two cases: and . Always solve both cases.
Another mistake is to forget that . If this relation is missed, the substitution becomes unclear. Rewrite the equation fully in terms of before solving.
Some students solve for the roots correctly but add them incorrectly. After obtaining , group negatives and positives carefully before summing.
Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.