Answer:
1. 7
2. undefined
3. 2/10=1/5
4. -4
Explanation:
The first 4 problems require you to know how to use the square root. Essentially, you want to find the number that times itself will equal the number in your square root. So, for the first problem, for some number x, x*x=49. Thus, x=7 and that is your answer.
For the second problem, we want to find a number x, such that x*x=-81. We know that two of the same number multiplied can not equal a negative, (unless you use imaginary) so this is undefined.
For the third problem, there is a rule that says that sqrt(4/100)=sqrt4/sqrt100. The sqrt of 4 is 2, and the sqrt of 100 is 10. So your answer is 2/10, which simplifies to 1/5
Finally, for the third problem, it is a cube root. So, you want to find the number x such that x*x*x=-64. This must be a negative number and after trial and error you can see the answer is -4.
Hope this clarifies any confusion you have!