The question asks that y is equal to 0. So the equation should be 0 = x² - 64. Now you can use the addition property of equality by adding 64 to both sides. This gives you x² = 64. Now, to find x, you need to find the root of 64, which is √64. However this can be simplified to a whole number 8. However, this isn't it. The answer actually can be 8 or -8, because -8² = 64 as well, because a negative multiplied by a negative is a positive. So your answer would be B. 8 or -8. Hope this helps. Feel free to ask questions about my explanation or any other questions you have.
