Solve: x² + 18x + 81 = 0. What is the factor form?
- (x + 8)²
- (x - 9)²
- (x + 9)²
- (x - 8)²
Explanation
:
- The first term is x^2, so .
- The last term is 81, so , which means (we take the positive root since the middle term is positive).
- The middle term is 18x. Let's check if it matches 2ab: . It does.
Therefore, the quadratic expression can be factored into .
So the factor form of the equation is .
Related MCQs
- 2x² + 4 = 9x
- 2x² + 9 = 4x
- 2x² + 9 = 4x
- x² + 4 = 9x
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