16Hit1600
Advanced MathVery hardProduct of the real solutions of a biquadratic

Advanced Math practice question

The equation x⁴ − 13x² + 36 = 0 has four real solutions. What is their product?

Answer: 36

x² = 4 or x² = 9, so x = ±2, ±3. The product (2)(−2)(3)(−3) = 36.

Common wrong answers

If you answered 0
0 is the sum of the solutions.
If you answered 13
13 is the sum of x² values.
If you answered -36
−36 miscounts the negative factors; there are two, so the product is positive.

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