To determine which of these quadratic equations can be solved by grouping, we look for quadratic equations that can be factored into a product of two binomials. This typically involves recognizing a common form or being able to rearrange the equation in a way that allows for grouping.
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\(x^2 + 8x - 22 = 0\)
- Cannot be easily factored; does not group nicely.
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\(x^2 + 10x + 21 = 0\)
- This can be factored as \((x + 3)(x + 7) = 0\) and therefore can be solved easily.
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\(x^2 - 4x - 8 = 0\)
- Cannot be factored nicely for grouping; does not rearrange.
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\(x^2 - 12x + 18 = 0\)
- This also cannot be factored nicely; does not group.
Conclusion: The quadratic equation that can be solved by grouping is \(x^2 + 10x + 21 = 0\).