If x² = 49, what is the value of x - 3?

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Multiple Choice

If x² = 49, what is the value of x - 3?

Explanation:
When you see x^2 = 49, the key idea is to take square roots. This tells you x = 7 or x = -7. Now look at x - 3 for each possibility: if x is 7, then x - 3 = 4; if x is -7, then x - 3 = -10. So there are two valid results: 4 and -10. Since the equation doesn’t specify which sign of x to take, both values can occur. The listed answer of -10 would correspond to using the negative root x = -7; the positive root would give 4.

When you see x^2 = 49, the key idea is to take square roots. This tells you x = 7 or x = -7. Now look at x - 3 for each possibility: if x is 7, then x - 3 = 4; if x is -7, then x - 3 = -10. So there are two valid results: 4 and -10. Since the equation doesn’t specify which sign of x to take, both values can occur. The listed answer of -10 would correspond to using the negative root x = -7; the positive root would give 4.

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