√-80 can be factored out, to see which factors can be square rooted. A pair of factors would be 16 and -5, so that would be 4√-5. But, negative numbers cannot be inside a square root. So, √-1 is the same thing as <em>i</em>, or <u>imaginary number</u>. So, the expression equivalent to √-80 is 4<em>i</em>√5. Have a nice day! ♪
