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Difficulty: 3/102024 NMTC 2024 (QII-56)

Compute the sum of all the roots of (2x+3)(x-4)+(2x+3)(x-6)=0

Guide / Hint

Hint 1: Do not expand the quadratic terms immediately. Notice the common factor .

Hint 2: Factor out and simplify the remaining expression inside the brackets.

Hint 3: Find the two roots of the resulting linear factors and add them together.

Solution

Step 1 (Factor out Common Term): We are given the equation:

Notice that is a common binomial factor in both terms. We factor it out:

Step 2 (Simplify the Equation): Combine the terms inside the bracket:

Dividing the second term by 2:

Step 3 (Find the Roots): Set each factor to zero:

Step 4 (Calculate Sum of Roots):

Step 5 (Conclusion): The sum of all the roots is exactly 3.5 (or 7/2).

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    2024 NMTC 2024 QII-56 - Olympiad Math Olympiad Question | Leminno