中等MATH-ALGE-010
Solve 2x^2 − 8 = 0.
A. x = 2 only
B. x = −2 only
C. x = 4 or x = −4
D. x = 2 or x = −2✓ 答案
解說
Divide by 2 to get x^2 = 4, so x = 2 or x = −2. A quadratic of this shape has two real roots unless the question restricts the variable. The values ±4 come from treating the equation as 2x − 8 = 0 or from forgetting the square.