The distance formula is the radical (x2-x1)2 + (y2-y1)^2. So for the x value, you subtract (-1) from 8. But be careful. It’s not 8-1. IT’S 8-(-1). Which x value, 9 should be squared. Which it is 81. The y value, you subtract 0 from 6. Which you should have 6 as your y value. Then, again you have to squared it. So, 6^2 is 36. Now that you have both of your x and y value, you have to subtract them again. In order to subtract, you subtract the y value from the x value. In other words, 81-36. The answer should be 45. But 45 is irrational. Because it can’t be rational under the radical form. So to simplified it, you have to find a number that is rational enough to get out from the inside of the radical form. The only number that would work is 9 and 5. So rad 9 is rational because it could escape from the inside. Which it’s 3 once it’s out. But, 5 is irrational and can’t go out. As a result, the answer is 3 rad 5. Or the 3 is outside of the radical form and 5 is the inside.