MCQEasyJEE 2026Quadratic Equations in Complex Numbers

JEE Mathematics 2026 Question with Solution

The sum of all the roots of the equation (x1)25x1+6=0(x-1)^2 - 5|x-1| + 6 = 0, is:

  • A

    55

  • B

    33

  • C

    44

  • D

    11

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: The equation is (x1)25x1+6=0(x-1)^2 - 5|x-1| + 6 = 0. We have to find the sum of all its roots.

Find: The sum of all values of xx satisfying the equation.

Use the substitution y=x1y = |x-1|. Since (x1)2=x12(x-1)^2 = |x-1|^2, the equation becomes

y25y+6=0y^2 - 5y + 6 = 0

Factoring,

(y2)(y3)=0(y-2)(y-3) = 0

So,

y=2ory=3y = 2 \quad \text{or} \quad y = 3

Now substitute back:

x1=2|x-1| = 2

which gives

x1=2x=3x-1 = 2 \Rightarrow x = 3

and

x1=2x=1x-1 = -2 \Rightarrow x = -1

Also,

x1=3|x-1| = 3

which gives

x1=3x=4x-1 = 3 \Rightarrow x = 4

and

x1=3x=2x-1 = -3 \Rightarrow x = -2

Thus the roots are 2,1,3,4-2, -1, 3, 4. Their sum is

(2)+(1)+3+4=4(-2)+(-1)+3+4 = 4

Therefore, the sum of all the roots is 44, so the correct option is C.

Using absolute value substitution

The key observation is that the equation contains both x1|x-1| and (x1)2(x-1)^2. Writing y=x1y = |x-1| converts it into a quadratic in one variable.

Then solve

y25y+6=0y^2 - 5y + 6 = 0

by factorization to get y=2y=2 and y=3y=3.

For each value of yy, solve the corresponding absolute value equation:

  • From x1=2|x-1|=2, the roots are x=3x=3 and x=1x=-1.
  • From x1=3|x-1|=3, the roots are x=4x=4 and x=2x=-2.

Adding all roots,

3+(1)+4+(2)=43 + (-1) + 4 + (-2) = 4

Hence, the required sum is 44.

Common mistakes

  • A common mistake is to treat x1=2|x-1| = 2 as giving only x1=2x-1=2. This is wrong because an absolute value equation u=k|u|=k gives two cases: u=ku=k and u=ku=-k. Always solve both cases.

  • Another mistake is to forget that (x1)2=x12(x-1)^2 = |x-1|^2. If this relation is missed, the substitution becomes unclear. Rewrite the equation fully in terms of y=x1y = |x-1| before solving.

  • Some students solve for the roots correctly but add them incorrectly. After obtaining 2,1,3,4-2, -1, 3, 4, group negatives and positives carefully before summing.

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