SAT Math: Find the Sum and Product of the Roots of 5x² - 15x - 7 = 0 (Vieta's Formulas)
By Vieta's formulas, sum of roots = -b/a = -(-15)/5 = 3.
Exact Question Text
What is the sum of the solutions to the quadratic equation 5x^2 - 15x - 7 = 0?
1. Step-by-Step Formal Solution
- In ax^2 + bx + c = 0, sum of roots = -b/a.
- a = 5, b = -15 => -(-15)/5 = 15/5 = 3.
2. Fast Desmos / Calculator Shortcut
Type solutions in Desmos using quadratic formula and add them: sum equals exactly 3.
3. Distractor Trap Analysis
- Trap A (Sign Flip): Forgetting to reverse inequality or dropping negative sign.
- Trap B (Partial Evaluation): Solving for intermediate variable and stopping early.
- Trap C (Extreme Assumption): Over-inferring beyond textual evidence.
- Option Correct: Accurately satisfies all algebraic and logical constraints.
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By Vieta's formulas, sum of roots = -b/a = -(-15)/5 = 3.
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